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Metadados em HTML</a></li><li><a href="/pt-BR/docs/Learn/HTML/Introduction_to_HTML/HTML_text_fundamentals">Fundamentos do texto em HTML</a></li><li><a href="/pt-BR/docs/Learn/HTML/Introduction_to_HTML/Creating_hyperlinks">Criando hyperlinks</a></li><li><a href="/pt-BR/docs/Learn/HTML/Introduction_to_HTML/Advanced_text_formatting">Formatação avançada de texto</a></li><li><a href="/pt-BR/docs/Learn/HTML/Introduction_to_HTML/Document_and_website_structure">Estrutura de documento e sites</a></li><li><a href="/pt-BR/docs/Learn/HTML/Introduction_to_HTML/Debugging_HTML">Debugging HTML</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/HTML/Introduction_to_HTML/Marking_up_a_letter">Marking up a letter</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/HTML/Introduction_to_HTML/Structuring_a_page_of_content">Structuring a page of content</a></li></ol></details></li><li><details><summary>Multimídia e incorporação</summary><ol><li><a href="/pt-BR/docs/Learn/HTML/Multimedia_and_embedding">Multimídia e Incorporação</a></li><li><a href="/pt-BR/docs/Learn/HTML/Multimedia_and_embedding/Images_in_HTML">Imagens no HTML</a></li><li><a href="/pt-BR/docs/Learn/HTML/Multimedia_and_embedding/Video_and_audio_content">Conteúdo de vídeo e áudio</a></li><li><a href="/pt-BR/docs/Learn/HTML/Multimedia_and_embedding/Other_embedding_technologies">Do objeto ao iframe - outras tecnologias de incorporação</a></li><li><a href="/pt-BR/docs/Learn/HTML/Multimedia_and_embedding/Adding_vector_graphics_to_the_Web">Adicionando vetor gráfico na web</a></li><li><a href="/pt-BR/docs/Learn/HTML/Multimedia_and_embedding/Responsive_images">Imagens responsivas</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/HTML/Multimedia_and_embedding/Mozilla_splash_page">Mozilla splash page</a></li></ol></details></li><li><details><summary>Tabelas HTML</summary><ol><li><a href="/pt-BR/docs/Learn/HTML/Tables">Tabelas em HTML</a></li><li><a href="/pt-BR/docs/Learn/HTML/Tables/Basics">HTML table basics</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/HTML/Tables/Advanced">HTML table advanced features and accessibility</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/HTML/Tables/Structuring_planet_data">Structuring planet data</a></li></ol></details></li><li class="section"><a href="/pt-BR/docs/Learn/CSS">CSS — Estilizando a Web</a></li><li><details><summary>CSS - primeiros passos</summary><ol><li><a href="/pt-BR/docs/Learn/CSS/First_steps">Primeiros passos com CSS</a></li><li><a href="/pt-BR/docs/Learn/CSS/First_steps/What_is_CSS">O que é CSS?</a></li><li><a href="/pt-BR/docs/Learn/CSS/First_steps/Getting_started">Iniciando com CSS</a></li><li><a href="/pt-BR/docs/Learn/CSS/First_steps/How_CSS_is_structured">Como CSS é estruturado</a></li><li><a href="/pt-BR/docs/Learn/CSS/First_steps/How_CSS_works">Como funciona o CSS</a></li><li><a href="/pt-BR/docs/Learn/CSS/First_steps/Styling_a_biography_page">Usando seu novo conhecimento</a></li></ol></details></li><li><details><summary>CSS building blocks</summary><ol><li><a href="/pt-BR/docs/Learn/CSS/Building_blocks">Construindo blocos CSS</a></li><li><a href="/pt-BR/docs/Learn/CSS/Building_blocks/Selectors">CSS selectors</a></li><li><a href="/pt-BR/docs/Learn/CSS/Building_blocks/Selectors/Type_Class_and_ID_Selectors">Seletores de tipo, classe e ID</a></li><li><a href="/pt-BR/docs/Learn/CSS/Building_blocks/Selectors/Attribute_selectors">Seletores de atributo</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Building_blocks/Selectors/Pseudo-classes_and_pseudo-elements">Pseudo-classes and pseudo-elements</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Building_blocks/Selectors/Combinators">Combinators</a></li><li><a href="/pt-BR/docs/Learn/CSS/Building_blocks/Cascade_and_inheritance">Cascata, especificidade e herança</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Building_blocks/Cascade_layers">Cascade layers</a></li><li><a href="/pt-BR/docs/Learn/CSS/Building_blocks/The_box_model">The box model</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Building_blocks/Backgrounds_and_borders">Backgrounds and borders</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Building_blocks/Handling_different_text_directions">Handling different text directions</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Building_blocks/Overflowing_content">Overflowing content</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Building_blocks/Values_and_units">CSS values and units</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Building_blocks/Sizing_items_in_CSS">Sizing items in CSS</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Building_blocks/Images_media_form_elements">Images, media, and form elements</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Building_blocks/Styling_tables">Styling tables</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Building_blocks/Advanced_styling_effects">Advanced styling effects</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Building_blocks/Debugging_CSS">Debugging CSS</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Building_blocks/Organizing">Organizing your CSS</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Building_blocks/Fundamental_CSS_comprehension">Fundamental CSS comprehension</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Building_blocks/Creating_fancy_letterheaded_paper">Creating fancy letterheaded paper</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Building_blocks/A_cool_looking_box">A cool-looking box</a></li></ol></details></li><li><details><summary>Estilização de textos</summary><ol><li><a href="/pt-BR/docs/Learn/CSS/Styling_text">Estilizando texto</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Styling_text/Fundamentals">Fundamental text and font styling</a></li><li><a href="/pt-BR/docs/Learn/CSS/Styling_text/Styling_lists">Manipulando Listas</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Styling_text/Styling_links">Styling links</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Styling_text/Web_fonts">Web fonts</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Styling_text/Typesetting_a_homepage">Typesetting a community school homepage</a></li></ol></details></li><li><details><summary>Esquemas CSS</summary><ol><li><a href="/pt-BR/docs/Learn/CSS/CSS_layout">CSS layout</a></li><li><a href="/pt-BR/docs/Learn/CSS/CSS_layout/Introduction">Introdução ao leiaute com CSS</a></li><li><a href="/pt-BR/docs/Learn/CSS/CSS_layout/Normal_Flow">Fluxo Normal</a></li><li><a href="/pt-BR/docs/Learn/CSS/CSS_layout/Flexbox">Flexbox</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/CSS_layout/Grids">Grids</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/CSS_layout/Floats">Floats</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/CSS_layout/Positioning">Positioning</a></li><li><a href="/pt-BR/docs/Learn/CSS/CSS_layout/Multiple-column_Layout">Layout de varias colunas</a></li><li><a href="/pt-BR/docs/Learn/CSS/CSS_layout/Responsive_Design">Design Responsivo</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/CSS_layout/Media_queries">Beginner's guide to media queries</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/CSS_layout/Legacy_Layout_Methods">Legacy layout methods</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/CSS_layout/Supporting_Older_Browsers">Supporting older browsers</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/CSS_layout/Fundamental_Layout_Comprehension">Fundamental layout comprehension</a></li></ol></details></li><li class="section"><a href="/pt-BR/docs/Learn/JavaScript">JavaScript — Uma linguagem de script dinâmica para aplicações cliente</a></li><li><details><summary>Primeiros passos com JavaScript</summary><ol><li><a href="/pt-BR/docs/Learn/JavaScript/First_steps">Primeiros passos com JavaScript</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/First_steps/What_is_JavaScript">O que é JavaScript?</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/First_steps/A_first_splash">Um primeiro mergulho no JavaScript</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/First_steps/What_went_wrong">O que deu errado? Resolvendo problemas no JavaScript</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/First_steps/Variables">Armazenando as informações que você precisa — Variáveis</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/First_steps/Math">Matemática básica no JavaScript — números e operadores</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/First_steps/Strings">Trabalhando com texto — strings em JavaScript</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/First_steps/Useful_string_methods">Métodos úteis de string</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/First_steps/Arrays">Arrays</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/First_steps/Silly_story_generator">Gerador de histórias bobas</a></li></ol></details></li><li><details><summary>Programando em JavaScript</summary><ol><li><a href="/pt-BR/docs/Learn/JavaScript/Building_blocks">Elementos construtivos do Javascript</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/Building_blocks/conditionals">Tomando decisões no seu código — condicionais</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/Building_blocks/Looping_code">Código em loop</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/Building_blocks/Functions">Funções — blocos reutilizáveis de código</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/Building_blocks/Build_your_own_function">Construa sua própria função</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/Building_blocks/Return_values">Valores de retorno de função</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/Building_blocks/Events">Introdução a eventos</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/Building_blocks/Event_bubbling">Comparativo entre Event Targets</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/Building_blocks/Image_gallery">Galeria de Imagens</a></li></ol></details></li><li><details><summary>Introdução Objetos em JavaScript</summary><ol><li><a href="/pt-BR/docs/Learn/JavaScript/Objects">Introdução a objetos em Javascript</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/Objects/Basics">O básico sobre objetos JavaScript</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/Objects/Object_prototypes">Protótipos de objetos</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/JavaScript/Objects/Object-oriented_programming">Object-oriented programming</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/Objects/Classes_in_JavaScript">Herança em JavaScript</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/Objects/JSON">Trabalhando com JSON</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/Objects/Object_building_practice">Prática de construção de objetos</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/Objects/Adding_bouncing_balls_features">Adicionando recursos à nossa demonstração de bolas pulantes</a></li></ol></details></li><li><details><summary>Asynchronous JavaScript</summary><ol><li><a href="/pt-BR/docs/Learn/JavaScript/Asynchronous">JavaScript Assíncrono</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/Asynchronous/Introducing">Introdução ao JavaScript Async</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/Asynchronous/Promises">Como usar Promises</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/JavaScript/Asynchronous/Implementing_a_promise-based_API">How to implement a promise-based API</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/JavaScript/Asynchronous/Introducing_workers">Introducing workers</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/JavaScript/Asynchronous/Sequencing_animations">Sequencing animations</a></li></ol></details></li><li><details open=""><summary>APIs Web na aplicação Cliente</summary><ol><li><a href="/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs">APIs web do lado cliente</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs/Introduction">Introdução às Web APIs</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs/Manipulating_documents">JavaScript e CSS</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs/Fetching_data">AJAX</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Third_party_APIs">Third-party APIs</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Drawing_graphics">Drawing graphics</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Video_and_audio_APIs">Video and Audio APIs</a></li><li><em><a href="/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs/Client-side_storage" aria-current="page">Client-side storage</a></em></li></ol></details></li><li class="section"><a href="/pt-BR/docs/Learn/Forms">Web forms — Working with user data</a></li><li><details><summary>Web form building blocks</summary><ol><li><a href="/pt-BR/docs/Learn/Forms">Formulários da Web - Trabalhando com dados do usuário</a></li><li><a href="/pt-BR/docs/Learn/Forms/Your_first_form">Meu primeiro formulário HTML</a></li><li><a href="/pt-BR/docs/Learn/Forms/How_to_structure_a_web_form">Como estruturar um formulário HTML</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Forms/Basic_native_form_controls">Basic native form controls</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Forms/HTML5_input_types">The HTML5 input types</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Forms/Other_form_controls">Other form controls</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Forms/Styling_web_forms">Styling web forms</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Forms/Advanced_form_styling">Advanced form styling</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Forms/UI_pseudo-classes">UI pseudo-classes</a></li><li><a href="/pt-BR/docs/Learn/Forms/Form_validation">Form data validation</a></li><li><a href="/pt-BR/docs/Learn/Forms/Sending_and_retrieving_form_data">Sending form data</a></li></ol></details></li><li><details><summary>Advanced web form techniques</summary><ol><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Forms/How_to_build_custom_form_controls">How to build custom form controls</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Forms/Sending_forms_through_JavaScript">Sending forms through JavaScript</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Forms/Property_compatibility_table_for_form_controls">CSS property compatibility table for form controls</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Forms/HTML_forms_in_legacy_browsers">HTML forms in legacy browsers</a></li></ol></details></li><li class="section"><a href="/pt-BR/docs/Learn/Accessibility">Acessibilidade — Faça a Internet usável por qualquer pessoa</a></li><li><details><summary>Guias de acessibilidade</summary><ol><li><a href="/pt-BR/docs/Learn/Accessibility">Accessibility</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Accessibility/What_is_accessibility">What is accessibility?</a></li><li><a href="/pt-BR/docs/Learn/Accessibility/HTML">HTML: Boas práticas em acessibilidade</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Accessibility/CSS_and_JavaScript">CSS and JavaScript accessibility best practices</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Accessibility/WAI-ARIA_basics">WAI-ARIA basics</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Accessibility/Multimedia">Accessible multimedia</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Accessibility/Mobile">Mobile accessibility</a></li><li><a href="/pt-BR/docs/Learn/Accessibility/Accessibility_troubleshooting">Avaliação: solucionando problemas de acessibilidade</a></li></ol></details></li><li class="section"><a href="/pt-BR/docs/Learn/Performance">Performance — Making websites fast and responsive</a></li><li><details><summary>Performance guides</summary><ol><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Performance">Web performance</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Performance/why_web_performance">The "why" of web performance</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Performance/What_is_web_performance">What is web performance?</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Performance/Perceived_performance">Perceived performance</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Performance/Measuring_performance">Measuring performance</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Performance/Multimedia">Multimedia: Images</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Performance/video">Multimedia: video</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Performance/JavaScript">JavaScript performance optimization</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Performance/HTML">HTML performance optimization</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Performance/CSS">CSS performance optimization</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Performance/business_case_for_performance">The business case for web performance</a></li></ol></details></li><li class="section"><a href="/pt-BR/docs/Learn/MathML">MathML — Writing mathematics with MathML</a></li><li><details><summary>MathML first steps</summary><ol><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/MathML/First_steps">MathML first steps</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/MathML/First_steps/Getting_started">Getting started with MathML</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/MathML/First_steps/Text_containers">MathML Text Containers</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/MathML/First_steps/Fractions_and_roots">MathML fractions and roots</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/MathML/First_steps/Scripts">MathML scripted elements</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/MathML/First_steps/Tables">MathML tables</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/MathML/First_steps/Three_famous_mathematical_formulas">Three famous mathematical formulas</a></li></ol></details></li><li class="section"><a href="/pt-BR/docs/Learn/../Games">Games — Developing games for the web</a></li><li><details><summary>Guides and tutorials</summary><ol><li><a href="/pt-BR/docs/Games/Introduction">Introdução ao desenvolvimento de jogos para a Web</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Games/Techniques">Techniques for game development</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Games/Tutorials">Tutorials</a></li><li><a href="/pt-BR/docs/Games/Publishing_games">Publishing games</a></li></ol></details></li><li class="section"><a href="/pt-BR/docs/Learn/Tools_and_testing">Ferramentas e teste</a></li><li><details><summary>Client-side web development tools</summary><ol><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools">Understanding client-side web development tools</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Overview">Client-side tooling overview</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Command_line">Command line crash course</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Package_management">Package management basics</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Introducing_complete_toolchain">Introducing a complete toolchain</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Deployment">Deploying our app</a></li></ol></details></li><li><details><summary>Introduction to client-side frameworks</summary><ol><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Introduction">Introduction to client-side frameworks</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Main_features">Framework main features</a></li></ol></details></li><li><details><summary>React</summary><ol><li><a href="/pt-BR/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_getting_started">Começando com React</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_todo_list_beginning">Beginning our React todo list</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_components">Componentizing our React app</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_interactivity_events_state">React interactivity: Events and state</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_interactivity_filtering_conditional_rendering">React interactivity: Editing, filtering, conditional rendering</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_accessibility">Accessibility in React</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_resources">React resources</a></li></ol></details></li><li><details><summary>Ember</summary><ol><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_getting_started">Getting started with Ember</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_structure_componentization">Ember app structure and componentization</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_interactivity_events_state">Ember interactivity: Events, classes and state</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_conditional_footer">Ember Interactivity: Footer functionality, conditional rendering</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_routing">Routing in Ember</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_resources">Ember resources and troubleshooting</a></li></ol></details></li><li><details><summary>Vue</summary><ol><li><a href="/pt-BR/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_getting_started">Iniciando com Vue</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_first_component">Creating our first Vue component</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_rendering_lists">Rendering a list of Vue components</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_methods_events_models">Adding a new todo form: Vue events, methods, and models</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_styling">Styling Vue components with CSS</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_computed_properties">Using Vue computed properties</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_conditional_rendering">Vue conditional rendering: editing existing todos</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_refs_focus_management">Vue refs and lifecycle methods for focus management</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_resources">Vue resources</a></li></ol></details></li><li><details><summary>Svelte</summary><ol><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_getting_started">Getting started with Svelte</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_Todo_list_beginning">Starting our Svelte to-do list app</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_variables_props">Dynamic behavior in Svelte: working with variables and props</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_components">Componentizing our Svelte app</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_reactivity_lifecycle_accessibility">Advanced Svelte: Reactivity, lifecycle, accessibility</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_stores">Working with Svelte stores</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_TypeScript">TypeScript support in Svelte</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_deployment_next">Deployment and next steps</a></li></ol></details></li><li><details><summary>Angular</summary><ol><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_getting_started">Getting started with Angular</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_todo_list_beginning">Beginning our Angular todo list app</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_styling">Styling our Angular app</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_item_component">Creating an item component</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_filtering">Filtering our to-do items</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_building">Building Angular applications and further resources</a></li></ol></details></li><li><details><summary>Git and GitHub</summary><ol><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/GitHub">Git and GitHub</a></li></ol></details></li><li><details><summary>Testes entre navegadores</summary><ol><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing">Cross browser testing</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Introduction">Introduction to cross-browser testing</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Testing_strategies">Strategies for carrying out testing</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/HTML_and_CSS">Handling common HTML and CSS problems</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/JavaScript">Handling common JavaScript problems</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Accessibility">Handling common accessibility problems</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Feature_detection">Implementing feature detection</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Automated_testing">Introduction to automated testing</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Your_own_automation_environment">Setting up your own test automation environment</a></li></ol></details></li><li class="section"><a href="/pt-BR/docs/Learn/Server-side">Programação de servidores de Aplicação</a></li><li><details><summary>Primeiros passos</summary><ol><li><a href="/pt-BR/docs/Learn/Server-side/First_steps">Primeiros passos programando o site no servidor</a></li><li><a href="/pt-BR/docs/Learn/Server-side/First_steps/Introduction">Introdução ao lado servidor</a></li><li><a href="/pt-BR/docs/Learn/Server-side/First_steps/Client-Server_overview">Visão geral do cliente-servidor</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Server-side/First_steps/Web_frameworks">Server-side web frameworks</a></li><li><a href="/pt-BR/docs/Learn/Server-side/First_steps/Website_security">Segurança em aplicação web</a></li></ol></details></li><li><details><summary>Framework Web Django (Python)</summary><ol><li><a href="/pt-BR/docs/Learn/Server-side/Django">Django Web Framework (Python)</a></li><li><a href="/pt-BR/docs/Learn/Server-side/Django/Introduction">Introdução ao Django</a></li><li><a href="/pt-BR/docs/Learn/Server-side/Django/development_environment">Configurando um ambiente de desenvolvimento Django</a></li><li><a href="/pt-BR/docs/Learn/Server-side/Django/Tutorial_local_library_website">Tutorial Django: Website da Biblioteca Local</a></li><li><a href="/pt-BR/docs/Learn/Server-side/Django/skeleton_website">Django Tutorial Parte 2: Criando o "esqueleto" de um site</a></li><li><a href="/pt-BR/docs/Learn/Server-side/Django/Models">Tutorial Django Parte 3: Usando models</a></li><li><a href="/pt-BR/docs/Learn/Server-side/Django/Admin_site">Tutorial Django Parte 4: Django admin site</a></li><li><a href="/pt-BR/docs/Learn/Server-side/Django/Home_page">Django Tutorial Parte 5: Criando nossa home page</a></li><li><a href="/pt-BR/docs/Learn/Server-side/Django/Generic_views">Tutorial Django Parte 6: Lista genérica e detail views</a></li><li><a href="/pt-BR/docs/Learn/Server-side/Django/Sessions">Tutorial Django Parte 7: Sessões</a></li><li><a href="/pt-BR/docs/Learn/Server-side/Django/Authentication">Tutorial Django Parte 8: Autenticação de usuário e permissões</a></li><li><a href="/pt-BR/docs/Learn/Server-side/Django/Forms">Tutorial Django Parte 9: Trabalhando com formulários</a></li><li><a href="/pt-BR/docs/Learn/Server-side/Django/Testing">Tutorial Django Parte 10: Testando uma aplicação web Django</a></li><li><a href="/pt-BR/docs/Learn/Server-side/Django/Deployment">Tutorial Django Parte 11: Hospedando Django para produção</a></li><li><a href="/pt-BR/docs/Learn/Server-side/Django/web_application_security">Segurança de aplicações web Django</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Server-side/Django/django_assessment_blog">Assessment: DIY Django mini blog</a></li></ol></details></li><li><details><summary>Framework Web Express (Node.js/JavaScript)</summary><ol><li><a href="/pt-BR/docs/Learn/Server-side/Express_Nodejs">Express Web Framework (Node.js/JavaScript)</a></li><li><a href="/pt-BR/docs/Learn/Server-side/Express_Nodejs/Introduction">Introdução Express/Node</a></li><li><a href="/pt-BR/docs/Learn/Server-side/Express_Nodejs/development_environment">Configurando o Node como ambiente de desenvolvimento</a></li><li><a href="/pt-BR/docs/Learn/Server-side/Express_Nodejs/Tutorial_local_library_website">Express: Tutorial para criar o site de uma Biblioteca Local</a></li><li><a href="/pt-BR/docs/Learn/Server-side/Express_Nodejs/skeleton_website">Express Tutorial Parte 2: Criando a estrutura do website</a></li><li><a href="/pt-BR/docs/Learn/Server-side/Express_Nodejs/mongoose">Tutorial Express Parte 3: Usando um banco de dados (com Mongoose)</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Server-side/Express_Nodejs/routes">Express Tutorial Part 4: Routes and controllers</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Server-side/Express_Nodejs/Displaying_data">Express Tutorial Part 5: Displaying library data</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Server-side/Express_Nodejs/forms">Express Tutorial Part 6: Working with forms</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Server-side/Express_Nodejs/deployment">Express Tutorial Part 7: Deploying to production</a></li></ol></details></li><li class="section"><a href="/pt-BR/docs/Learn/Common_questions">Mais recursos</a></li><li><details><summary>Questões gerais</summary><ol><li><a href="/pt-BR/docs/Learn/Common_questions">Questões comuns</a></li><li><a href="/pt-BR/docs/Learn/HTML/Howto">Use HTML para resolver problemas comuns</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/CSS/Howto">Use CSS to solve common problems</a></li><li><a href="/pt-BR/docs/Learn/JavaScript/Howto">Solve common problems in your JavaScript code</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Common_questions/Web_mechanics">Web mechanics</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Common_questions/Tools_and_setup">Tools and setup</a></li><li><a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Learn/Common_questions/Design_and_accessibility">Design and accessibility</a></li></ol></details></li></ol></div></div><section class="place side"></section></nav></aside><div class="toc-container"><aside class="toc"><nav><div class="document-toc-container"><section class="document-toc"><header><h2 class="document-toc-heading">Neste artigo</h2></header><ul class="document-toc-list"><li class="document-toc-item "><a class="document-toc-link" href="#armazenamento_do_lado_do_cliente">Armazenamento do lado do cliente?</a></li><li class="document-toc-item "><a class="document-toc-link" href="#storing_simple_data_—_web_storage">Storing simple data — web storage</a></li><li class="document-toc-item "><a class="document-toc-link" href="#storing_complex_data_—_indexeddb">Storing complex data — IndexedDB</a></li><li class="document-toc-item "><a class="document-toc-link" href="#offline_asset_storage">Offline asset storage</a></li><li class="document-toc-item "><a class="document-toc-link" href="#summary">Summary</a></li><li class="document-toc-item "><a class="document-toc-link" href="#see_also">See also</a></li></ul></section></div></nav></aside><section class="place side"></section></div></div><main id="content" class="main-content "><article class="main-page-content" lang="pt-BR"><header><h1>Client-side storage</h1></header><div class="section-content"><ul class="prev-next"> <li><a class="button secondary only-in-en-us" href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Video_and_audio_APIs" title="Esta página está disponível apenas em inglês no momento"><span class="button-wrap"> Anterior </span></a></li> <li><a class="button secondary" href="/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs"><span class="button-wrap"> Menu: APIs web do lado cliente</span></a></li> </ul> <p>Os navegadores modernos oferecem suporte a várias maneiras de os sites armazenarem dados no computador do usuário - com a permissão do usuário - e depois recuperá-los quando necessário. Isso permite que você mantenha dados para armazenamento de longo prazo, salve sites ou documentos para uso offline, retenha configurações específicas do usuário para seu site e muito mais. Este artigo explica os princípios básicos de como eles funcionam.</p> <figure class="table-container"><table class="learn-box standard-table"> <tbody> <tr> <th scope="row">Pré-requisitos:</th> <td> Noções básicas de JavaScript (consulte as <a href="/pt-BR/docs/Learn/JavaScript/First_steps">primeiras etapas </a><a href="/pt-BR/docs/Learn/JavaScript/First_steps"></a>, <a href="/pt-BR/docs/Learn/JavaScript/Building_blocks">blocos de construção</a> , <a href="/pt-BR/docs/Learn/JavaScript/Objects">objetos JavaScript</a> ), as <a href="/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs/Introduction">noções básicas de APIs do lado do cliente</a> </td> </tr> <tr> <th scope="row">Objetivo:</th> <td> Para aprender como usar APIs de armazenamento do lado do cliente para armazenar dados de aplicativos </td> </tr> </tbody> </table></figure></div><section aria-labelledby="armazenamento_do_lado_do_cliente"><h2 id="armazenamento_do_lado_do_cliente"><a href="#armazenamento_do_lado_do_cliente">Armazenamento do lado do cliente?</a></h2><div class="section-content"><p>Em outro lugar na área de aprendizagem MDN, falamos sobre a diferença entre <a href="/pt-BR/docs/Learn/Server-side/First_steps/Client-Server_overview#static_sites">sites estáticos</a> e <a href="/pt-BR/docs/Learn/Server-side/First_steps/Client-Server_overview#dynamic_sites">sites dinâmicos</a> . A maioria dos principais sites modernos são dinâmicos - eles armazenam dados no servidor usando algum tipo de banco de dados (armazenamento do lado do servidor) e, em seguida, executam o código do <a href="/pt-BR/docs/Learn/Server-side">lado do servidor</a> para recuperar os dados necessários, inserem-nos em modelos de página estática e fornecem o HTML resultante para o cliente a ser exibido pelo navegador do usuário.er.</p> <p>O armazenamento do lado do cliente funciona em princípios semelhantes, mas tem usos diferentes. Consiste em APIs JavaScript que permitem armazenar dados no cliente (ou seja, na máquina do usuário) e recuperá-los quando necessário. Isso tem muitos usos distintos, como:</p> <ul> <li>Personalizar as preferências do site (por exemplo, mostrar a escolha do usuário de widgets personalizados, esquema de cores ou tamanho da fonte).</li> <li>Atividade anterior persistente do site (por exemplo, armazenar o conteúdo de um carrinho de compras de uma sessão anterior, lembrando se um usuário estava conectado anteriormente).</li> <li>Salvar dados e ativos localmente para que o download de um site seja mais rápido (e potencialmente mais barato) ou possa ser usado sem uma conexão de rede.</li> <li>Salvar documentos gerados por aplicativos da web localmente para uso offline</li> </ul> <p>Freqüentemente, o armazenamento do lado do cliente e do lado do servidor são usados juntos. Por exemplo, você pode baixar um lote de arquivos de música (talvez usados por um jogo da web ou aplicativo de reprodutor de música), armazená-los em um banco de dados do cliente e reproduzi-los conforme necessário. O usuário só teria que baixar os arquivos de música uma vez - em visitas subsequentes, eles seriam recuperados do banco de dados.</p> <div class="notecard note"> <p><strong>Nota:</strong> : Existem limites para a quantidade de dados que você pode armazenar usando APIs de armazenamento do lado do cliente (possivelmente por API individual e cumulativamente); o limite exato varia dependendo do navegador e, possivelmente, com base nas configurações do usuário. Consulte <a href="/en-US/docs/Web/API/Storage_API/Storage_quotas_and_eviction_criteria" class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento">Limites de armazenamento do navegador e critérios de despejo</a> para obter mais informações..</p> </div></div></section><section aria-labelledby="old_school_cookies"><h3 id="old_school_cookies"><a href="#old_school_cookies">Old school: Cookies</a></h3><div class="section-content"><p>The concept of client-side storage has been around for <strong>Nota</strong> : Existem limites para a quantidade de dados que você pode armazenar usando APIs de armazenamento do lado do cliente (possivelmente por API individual e cumulativamente); o limite exato varia dependendo do navegador e, possivelmente, com base nas configurações do usuário. Consultea long time. Since the early days of the web, sites have used <a href="/pt-BR/docs/Web/HTTP/Cookies">cookies</a> to store information to personalize user experience on websites. They're the earliest form of client-side storage commonly used on the web.</p> <p>These days, there are easier mechanisms available for storing client-side data, therefore we won't be teaching you how to use cookies in this article. However, this does not mean cookies are completely useless on the modern-day web — they are still used commonly to store data related to user personalization and state, e.g. session IDs and access tokens. For more information on cookies see our <a href="/pt-BR/docs/Web/HTTP/Cookies">Using HTTP cookies</a> article.</p></div></section><section aria-labelledby="new_school_web_storage_and_indexeddb"><h3 id="new_school_web_storage_and_indexeddb"><a href="#new_school_web_storage_and_indexeddb">New school: Web Storage and IndexedDB</a></h3><div class="section-content"><p>The "easier" features we mentioned above are as follows:</p> <ul> <li>The <a href="/pt-BR/docs/Web/API/Web_Storage_API">Web Storage API</a> provides a very simple syntax for storing and retrieving smaller, data items consisting of a name and a corresponding value. This is useful when you just need to store some simple data, like the user's name, whether they are logged in, what color to use for the background of the screen, etc.</li> <li>The <a href="/pt-BR/docs/Web/API/IndexedDB_API">IndexedDB API</a> provides the browser with a complete database system for storing complex data. This can be used for things from complete sets of customer records to even complex data types like audio or video files.</li> </ul> <p>You'll learn more about these APIs below.</p></div></section><section aria-labelledby="the_future_cache_api"><h3 id="the_future_cache_api"><a href="#the_future_cache_api">The future: Cache API</a></h3><div class="section-content"><p>Some modern browsers support the new <a href="/pt-BR/docs/Web/API/Cache"><code>Cache</code></a> API. This API is designed for storing HTTP responses to specific requests, and is very useful for doing things like storing website assets offline so the site can subsequently be used without a network connection. Cache is usually used in combination with the <a href="/pt-BR/docs/Web/API/Service_Worker_API">Service Worker API</a>, although it doesn't have to be.</p> <p>Use of Cache and Service Workers is an advanced topic, and we won't be covering it in great detail in this article, although we will show a simple example in the <a href="#offline_asset_storage">Offline asset storage</a> section below.</p></div></section><section aria-labelledby="storing_simple_data_—_web_storage"><h2 id="storing_simple_data_—_web_storage"><a href="#storing_simple_data_—_web_storage">Storing simple data — web storage</a></h2><div class="section-content"><p>The <a href="/pt-BR/docs/Web/API/Web_Storage_API">Web Storage API</a> is very easy to use — you store simple name/value pairs of data (limited to strings, numbers, etc.) and retrieve these values when needed.</p></div></section><section aria-labelledby="basic_syntax"><h3 id="basic_syntax"><a href="#basic_syntax">Basic syntax</a></h3><div class="section-content"><p>Let's show you how:</p> <ol> <li> <p>First, go to our <a href="https://mdn.github.io/learning-area/javascript/apis/client-side-storage/web-storage/index.html" class="external" target="_blank">web storage blank template</a> on GitHub (open this in a new tab).</p> </li> <li> <p>Open the JavaScript console of your browser's developer tools.</p> </li> <li> <p>All of your web storage data is contained within two object-like structures inside the browser: <a href="/pt-BR/docs/Web/API/Window/sessionStorage" title="sessionStorage"><code>sessionStorage</code></a> and <a href="/pt-BR/docs/Web/API/Window/localStorage" title="localStorage"><code>localStorage</code></a>. The first one persists data for as long as the browser is open (the data is lost when the browser is closed) and the second one persists data even after the browser is closed and then opened again. We'll use the second one in this article as it is generally more useful.</p> <p>The <a href="/pt-BR/docs/Web/API/Storage/setItem"><code>Storage.setItem()</code></a> method allows you to save a data item in storage — it takes two parameters: the name of the item, and its value. Try typing this into your JavaScript console (change the value to your own name, if you wish!):</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>localStorage.setItem("name", "Chris"); </code></pre></div> </li> <li> <p>The <a href="/pt-BR/docs/Web/API/Storage/getItem"><code>Storage.getItem()</code></a> method takes one parameter — the name of a data item you want to retrieve — and returns the item's value. Now type these lines into your JavaScript console:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>let myName = localStorage.getItem("name"); myName; </code></pre></div> <p>Upon typing in the second line, you should see that the <code>myName</code> variable now contains the value of the <code>name</code> data item.</p> </li> <li> <p>The <a href="/pt-BR/docs/Web/API/Storage/removeItem"><code>Storage.removeItem()</code></a> method takes one parameter — the name of a data item you want to remove — and removes that item out of web storage. Type the following lines into your JavaScript console:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>localStorage.removeItem("name"); let myName = localStorage.getItem("name"); myName; </code></pre></div> <p>The third line should now return <code>null</code> — the <code>name</code> item no longer exists in the web storage.</p> </li> </ol></div></section><section aria-labelledby="the_data_persists!"><h3 id="the_data_persists!"><a href="#the_data_persists!">The data persists!</a></h3><div class="section-content"><p>One key feature of web storage is that the data persists between page loads (and even when the browser is shut down, in the case of <code>localStorage</code>). Let's look at this in action.</p> <ol> <li> <p>Open our web storage blank template again, but this time in a different browser to the one you've got this tutorial open in! This will make it easier to deal with.</p> </li> <li> <p>Type these lines into the browser's JavaScript console:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>localStorage.setItem("name", "Chris"); let myName = localStorage.getItem("name"); myName; </code></pre></div> <p>You should see the name item returned.</p> </li> <li> <p>Now close down the browser and open it up again.</p> </li> <li> <p>Enter the following lines again:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>let myName = localStorage.getItem("name"); myName; </code></pre></div> <p>You should see that the value is still available, even though the browser has been closed and then opened again.</p> </li> </ol></div></section><section aria-labelledby="separate_storage_for_each_domain"><h3 id="separate_storage_for_each_domain"><a href="#separate_storage_for_each_domain">Separate storage for each domain</a></h3><div class="section-content"><p>There is a separate data store for each domain (each separate web address loaded in the browser). You will see that if you load two websites (say google.com and amazon.com) and try storing an item on one website, it won't be available to the other website.</p> <p>This makes sense — you can imagine the security issues that would arise if websites could see each other's data!</p></div></section><section aria-labelledby="a_more_involved_example"><h3 id="a_more_involved_example"><a href="#a_more_involved_example">A more involved example</a></h3><div class="section-content"><p>Let's apply this new-found knowledge by writing a simple working example to give you an idea of how web storage can be used. Our example will allow you enter a name, after which the page will update to give you a personalized greeting. This state will also persist across page/browser reloads, because the name is stored in web storage.</p> <p>You can find the example HTML at <a href="https://github.com/mdn/learning-area/blob/master/javascript/apis/client-side-storage/web-storage/personal-greeting.html" class="external" target="_blank">personal-greeting.html</a> — this contains a simple website with a header, content, and footer, and a form for entering your name.</p> <p> <img src="/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs/Client-side_storage/web-storage-demo.png" alt="" width="1024" height="550" loading="lazy"> </p> <p>Let's build up the example, so you can understand how it works.</p> <ol> <li> <p>First, make a local copy of our <a href="https://github.com/mdn/learning-area/blob/master/javascript/apis/client-side-storage/web-storage/personal-greeting.html" class="external" target="_blank">personal-greeting.html</a> file in a new directory on your computer.</p> </li> <li> <p>Next, note how our HTML references a JavaScript file called <code>index.js</code> (see line 40). We need to create this and write our JavaScript code into it. Create an <code>index.js</code> file in the same directory as your HTML file.</p> </li> <li> <p>We'll start off by creating references to all the HTML features we need to manipulate in this example — we'll create them all as constants, as these references do not need to change in the lifecycle of the app. Add the following lines to your JavaScript file:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>// create needed constants const rememberDiv = document.querySelector(".remember"); const forgetDiv = document.querySelector(".forget"); const form = document.querySelector("form"); const nameInput = document.querySelector("#entername"); const submitBtn = document.querySelector("#submitname"); const forgetBtn = document.querySelector("#forgetname"); const h1 = document.querySelector("h1"); const personalGreeting = document.querySelector(".personal-greeting"); </code></pre></div> </li> <li> <p>Next up, we need to include a small event listener to stop the form from actually submitting itself when the submit button is pressed, as this is not the behavior we want. Add this snippet below your previous code:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>// Stop the form from submitting when a button is pressed form.addEventListener("submit", function (e) { e.preventDefault(); }); </code></pre></div> </li> <li> <p>Now we need to add an event listener, the handler function of which will run when the "Say hello" button is clicked. The comments explain in detail what each bit does, but in essence here we are taking the name the user has entered into the text input box and saving it in web storage using <code>setItem()</code>, then running a function called <code>nameDisplayCheck()</code> that will handle updating the actual website text. Add this to the bottom of your code:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>// run function when the 'Say hello' button is clicked submitBtn.addEventListener("click", function () { // store the entered name in web storage localStorage.setItem("name", nameInput.value); // run nameDisplayCheck() to sort out displaying the // personalized greetings and updating the form display nameDisplayCheck(); }); </code></pre></div> </li> <li> <p>At this point we also need an event handler to run a function when the "Forget" button is clicked — this is only displayed after the "Say hello" button has been clicked (the two form states toggle back and forth). In this function we remove the <code>name</code> item from web storage using <code>removeItem()</code>, then again run <code>nameDisplayCheck()</code> to update the display. Add this to the bottom:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>// run function when the 'Forget' button is clicked forgetBtn.addEventListener("click", function () { // Remove the stored name from web storage localStorage.removeItem("name"); // run nameDisplayCheck() to sort out displaying the // generic greeting again and updating the form display nameDisplayCheck(); }); </code></pre></div> </li> <li> <p>It is now time to define the <code>nameDisplayCheck()</code> function itself. Here we check whether the name item has been stored in web storage by using <code>localStorage.getItem('name')</code> as a conditional test. If it has been stored, this call will evaluate to <code>true</code>; if not, it will be <code>false</code>. If it is <code>true</code>, we display a personalized greeting, display the "forget" part of the form, and hide the "Say hello" part of the form. If it is <code>false</code>, we display a generic greeting and do the opposite. Again, put the following code at the bottom:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>// define the nameDisplayCheck() function function nameDisplayCheck() { // check whether the 'name' data item is stored in web Storage if (localStorage.getItem("name")) { // If it is, display personalized greeting let name = localStorage.getItem("name"); h1.textContent = "Welcome, " + name; personalGreeting.textContent = "Welcome to our website, " + name + "! We hope you have fun while you are here."; // hide the 'remember' part of the form and show the 'forget' part forgetDiv.style.display = "block"; rememberDiv.style.display = "none"; } else { // if not, display generic greeting h1.textContent = "Welcome to our website "; personalGreeting.textContent = "Welcome to our website. We hope you have fun while you are here."; // hide the 'forget' part of the form and show the 'remember' part forgetDiv.style.display = "none"; rememberDiv.style.display = "block"; } } </code></pre></div> </li> <li> <p>Last but not least, we need to run the <code>nameDisplayCheck()</code> function every time the page is loaded. If we don't do this, then the personalized greeting will not persist across page reloads. Add the following to the bottom of your code:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>document.body.onload = nameDisplayCheck; </code></pre></div> </li> </ol> <p>Your example is finished — well done! All that remains now is to save your code and test your HTML page in a browser. You can see our <a href="https://mdn.github.io/learning-area/javascript/apis/client-side-storage/web-storage/personal-greeting.html" class="external" target="_blank">finished version running live here</a>.</p> <div class="notecard note"> <p><strong>Nota:</strong> There is another, slightly more complex example to explore at <a href="/pt-BR/docs/Web/API/Web_Storage_API/Using_the_Web_Storage_API">Using the Web Storage API</a>.</p> </div> <div class="notecard note"> <p><strong>Nota:</strong> In the line <code><script src="index.js" defer></script></code> of the source for our finished version, the <code>defer</code> attribute specifies that the contents of the <a href="/pt-BR/docs/Web/HTML/Element/script"><code><script></code></a> element will not execute until the page has finished loading.</p> </div></div></section><section aria-labelledby="storing_complex_data_—_indexeddb"><h2 id="storing_complex_data_—_indexeddb"><a href="#storing_complex_data_—_indexeddb">Storing complex data — IndexedDB</a></h2><div class="section-content"><p>The <a href="/pt-BR/docs/Web/API/IndexedDB_API">IndexedDB API</a> (sometimes abbreviated IDB) is a complete database system available in the browser in which you can store complex related data, the types of which aren't limited to simple values like strings or numbers. You can store videos, images, and pretty much anything else in an IndexedDB instance.</p> <p>However, this does come at a cost: IndexedDB is much more complex to use than the Web Storage API. In this section, we'll really only scratch the surface of what it is capable of, but we will give you enough to get started.</p></div></section><section aria-labelledby="working_through_a_note_storage_example"><h3 id="working_through_a_note_storage_example"><a href="#working_through_a_note_storage_example">Working through a note storage example</a></h3><div class="section-content"><p>Here we'll run you through an example that allows you to store notes in your browser and view and delete them whenever you like, getting you to build it up for yourself and explaining the most fundamental parts of IDB as we go along.</p> <p>The app looks something like this:</p> <p> <img src="/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs/Client-side_storage/idb-demo.png" alt="" width="803" height="736" loading="lazy"> </p> <p>Each note has a title and some body text, each individually editable. The JavaScript code we'll go through below has detailed comments to help you understand what's going on.</p></div></section><section aria-labelledby="getting_started"><h3 id="getting_started"><a href="#getting_started">Getting started</a></h3><div class="section-content"><ol> <li>First of all, make local copies of our <a href="https://github.com/mdn/learning-area/blob/master/javascript/apis/client-side-storage/indexeddb/notes/index.html" class="external" target="_blank"><code>index.html</code></a>, <a href="https://github.com/mdn/learning-area/blob/master/javascript/apis/client-side-storage/indexeddb/notes/style.css" class="external" target="_blank"><code>style.css</code></a>, and <a href="https://github.com/mdn/learning-area/blob/master/javascript/apis/client-side-storage/indexeddb/notes/index-start.js" class="external" target="_blank"><code>index-start.js</code></a> files into a new directory on your local machine.</li> <li>Have a look at the files. You'll see that the HTML is pretty simple: a web site with a header and footer, as well as a main content area that contains a place to display notes, and a form for entering new notes into the database. The CSS provides some simple styling to make it clearer what is going on. The JavaScript file contains five declared constants containing references to the <a href="/pt-BR/docs/Web/HTML/Element/ul"><code><ul></code></a> element the notes will be displayed in, the title and body <a href="/pt-BR/docs/Web/HTML/Element/input"><code><input></code></a> elements, the <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/HTML/Element/form"><code><form></code></a> itself, and the <a href="/pt-BR/docs/Web/HTML/Element/button"><code><button></code></a>.</li> <li>Rename your JavaScript file to <code>index.js</code>. You are now ready to start adding code to it.</li> </ol></div></section><section aria-labelledby="database_initial_set_up"><h3 id="database_initial_set_up"><a href="#database_initial_set_up">Database initial set up</a></h3><div class="section-content"><p>Now let's look at what we have to do in the first place, to actually set up a database.</p> <ol> <li> <p>Below the constant declarations, add the following lines:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>// Create an instance of a db object for us to store the open database in let db; </code></pre></div> <p>Here we are declaring a variable called <code>db</code> — this will later be used to store an object representing our database. We will use this in a few places, so we've declared it globally here to make things easier.</p> </li> <li> <p>Next, add the following to the bottom of your code:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>window.onload = function () {}; </code></pre></div> <p>We will write all of our subsequent code inside this <code>window.onload</code> event handler function, called when the window's <a href="/pt-BR/docs/Web/API/Window/load_event"><code>load</code></a> event fires, to make sure we don't try to use IndexedDB functionality before the app has completely finished loading (it could fail if we don't).</p> </li> <li> <p>Inside the <code>window.onload</code> handler, add the following:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>// Open our database; it is created if it doesn't already exist // (see onupgradeneeded below) let request = window.indexedDB.open("notes_db", 1); </code></pre></div> <p>This line creates a <code>request</code> to open version <code>1</code> of a database called <code>notes_db</code>. If this doesn't already exist, it will be created for you by subsequent code. You will see this request pattern used very often throughout IndexedDB. Database operations take time. You don't want to hang the browser while you wait for the results, so database operations are <a href="/pt-BR/docs/Glossary/Asynchronous">asynchronous</a>, meaning that instead of happening immediately, they will happen at some point in the future, and you get notified when they're done.</p> <p>To handle this in IndexedDB, you create a request object (which can be called anything you like — we called it <code>request</code> so it is obvious what it is for). You then use event handlers to run code when the request completes, fails, etc., which you'll see in use below.</p> <div class="notecard note"> <p><strong>Nota:</strong> The version number is important. If you want to upgrade your database (for example, by changing the table structure), you have to run your code again with an increased version number, different schema specified inside the <code>onupgradeneeded</code> handler (see below), etc. We won't cover upgrading databases in this simple tutorial.</p> </div> </li> <li> <p>Now add the following event handlers just below your previous addition — again inside the <code>window.onload</code> handler:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>// onerror handler signifies that the database didn't open successfully request.onerror = function () { console.log("Database failed to open"); }; // onsuccess handler signifies that the database opened successfully request.onsuccess = function () { console.log("Database opened successfully"); // Store the opened database object in the db variable. This is used a lot below db = request.result; // Run the displayData() function to display the notes already in the IDB displayData(); }; </code></pre></div> <p>The <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/IDBRequest/error_event"><code>request.onerror</code></a> handler will run if the system comes back saying that the request failed. This allows you to respond to this problem. In our simple example, we just print a message to the JavaScript console.</p> <p>The <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/IDBRequest/success_event"><code>request.onsuccess</code></a> handler on the other hand will run if the request returns successfully, meaning the database was successfully opened. If this is the case, an object representing the opened database becomes available in the <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/IDBRequest/result"><code>request.result</code></a> property, allowing us to manipulate the database. We store this in the <code>db</code> variable we created earlier for later use. We also run a custom function called <code>displayData()</code>, which displays the data in the database inside the <a href="/pt-BR/docs/Web/HTML/Element/ul"><code><ul></code></a>. We run it now so that the notes already in the database are displayed as soon as the page loads. You'll see this defined later on.</p> </li> <li> <p>Finally for this section, we'll add probably the most important event handler for setting up the database: <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/IDBOpenDBRequest/upgradeneeded_event"><code>request.onupgradeneeded</code></a>. This handler runs if the database has not already been set up, or if the database is opened with a bigger version number than the existing stored database (when performing an upgrade). Add the following code, below your previous handler:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>// Setup the database tables if this has not already been done request.onupgradeneeded = function (e) { // Grab a reference to the opened database let db = e.target.result; // Create an objectStore to store our notes in (basically like a single table) // including a auto-incrementing key let objectStore = db.createObjectStore("notes_os", { keyPath: "id", autoIncrement: true, }); // Define what data items the objectStore will contain objectStore.createIndex("title", "title", { unique: false }); objectStore.createIndex("body", "body", { unique: false }); console.log("Database setup complete"); }; </code></pre></div> <p>This is where we define the schema (structure) of our database; that is, the set of columns (or fields) it contains. Here we first grab a reference to the existing database from the <code>result</code> property of the event's target (<code>e.target.result</code>), which is the <code>request</code> object. This is equivalent to the line <code>db = request.result;</code> inside the <code>onsuccess</code> handler, but we need to do this separately here because the <code>onupgradeneeded</code> handler (if needed) will run before the <code>onsuccess</code> handler, meaning that the <code>db</code> value wouldn't be available if we didn't do this.</p> <p>We then use <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/IDBDatabase/createObjectStore"><code>IDBDatabase.createObjectStore()</code></a> to create a new object store inside our opened database called <code>notes_os</code>. This is equivalent to a single table in a conventional database system. We've given it the name notes, and also specified an <code>autoIncrement</code> key field called <code>id</code> — in each new record this will automatically be given an incremented value — the developer doesn't need to set this explicitly. Being the key, the <code>id</code> field will be used to uniquely identify records, such as when deleting or displaying a record.</p> <p>We also create two other indexes (fields) using the <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/IDBObjectStore/createIndex"><code>IDBObjectStore.createIndex()</code></a> method: <code>title</code> (which will contain a title for each note), and <code>body</code> (which will contain the body text of the note).</p> </li> </ol> <p>So with this simple database schema set up, when we start adding records to the database; each one will be represented as an object along these lines:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>{ title: "Buy milk", body: "Need both cows milk and soy.", id: 8 } </code></pre></div></div></section><section aria-labelledby="adding_data_to_the_database"><h3 id="adding_data_to_the_database"><a href="#adding_data_to_the_database">Adding data to the database</a></h3><div class="section-content"><p>Now let's look at how we can add records to the database. This will be done using the form on our page.</p> <p>Below your previous event handler (but still inside the <code>window.onload</code> handler), add the following line, which sets up an <code>onsubmit</code> handler that runs a function called <code>addData()</code> when the form is submitted (when the submit <a href="/pt-BR/docs/Web/HTML/Element/button"><code><button></code></a> is pressed leading to a successful form submission):</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>// Create an onsubmit handler so that when the form is submitted the addData() function is run form.onsubmit = addData; </code></pre></div> <p>Now let's define the <code>addData()</code> function. Add this below your previous line:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>// Define the addData() function function addData(e) { // prevent default - we don't want the form to submit in the conventional way e.preventDefault(); // grab the values entered into the form fields and store them in an object ready for being inserted into the DB let newItem = { title: titleInput.value, body: bodyInput.value }; // open a read/write db transaction, ready for adding the data let transaction = db.transaction(["notes_os"], "readwrite"); // call an object store that's already been added to the database let objectStore = transaction.objectStore("notes_os"); // Make a request to add our newItem object to the object store let request = objectStore.add(newItem); request.onsuccess = function () { // Clear the form, ready for adding the next entry titleInput.value = ""; bodyInput.value = ""; }; // Report on the success of the transaction completing, when everything is done transaction.oncomplete = function () { console.log("Transaction completed: database modification finished."); // update the display of data to show the newly added item, by running displayData() again. displayData(); }; transaction.onerror = function () { console.log("Transaction not opened due to error"); }; } </code></pre></div> <p>This is quite complex; breaking it down, we:</p> <ul> <li>Run <a href="/pt-BR/docs/Web/API/Event/preventDefault"><code>Event.preventDefault()</code></a> on the event object to stop the form actually submitting in the conventional manner (this would cause a page refresh and spoil the experience).</li> <li>Create an object representing a record to enter into the database, populating it with values from the form inputs. note that we don't have to explicitly include an <code>id</code> value — as we explained earlier, this is auto-populated.</li> <li>Open a <code>readwrite</code> transaction against the <code>notes_os</code> object store using the <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/IDBDatabase/transaction"><code>IDBDatabase.transaction()</code></a> method. This transaction object allows us to access the object store so we can do something to it, e.g. add a new record.</li> <li>Access the object store using the <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/IDBTransaction/objectStore"><code>IDBTransaction.objectStore()</code></a> method, saving the result in the <code>objectStore</code> variable.</li> <li>Add the new record to the database using <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/IDBObjectStore/add"><code>IDBObjectStore.add()</code></a>. This creates a request object, in the same fashion as we've seen before.</li> <li>Add a bunch of event handlers to the <code>request</code> and the <code>transaction</code> to run code at critical points in the lifecycle. Once the request has succeeded, we clear the form inputs ready for entering the next note. Once the transaction has completed, we run the <code>displayData()</code> function again to update the display of notes on the page.</li> </ul></div></section><section aria-labelledby="displaying_the_data"><h3 id="displaying_the_data"><a href="#displaying_the_data">Displaying the data</a></h3><div class="section-content"><p>We've referenced <code>displayData()</code> twice in our code already, so we'd probably better define it. Add this to your code, below the previous function definition:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>// Define the displayData() function function displayData() { // Here we empty the contents of the list element each time the display is updated // If you didn't do this, you'd get duplicates listed each time a new note is added while (list.firstChild) { list.removeChild(list.firstChild); } // Open our object store and then get a cursor - which iterates through all the // different data items in the store let objectStore = db.transaction("notes_os").objectStore("notes_os"); objectStore.openCursor().onsuccess = function (e) { // Get a reference to the cursor let cursor = e.target.result; // If there is still another data item to iterate through, keep running this code if (cursor) { // Create a list item, h3, and p to put each data item inside when displaying it // structure the HTML fragment, and append it inside the list const listItem = document.createElement("li"); const h3 = document.createElement("h3"); const para = document.createElement("p"); listItem.appendChild(h3); listItem.appendChild(para); list.appendChild(listItem); // Put the data from the cursor inside the h3 and para h3.textContent = cursor.value.title; para.textContent = cursor.value.body; // Store the ID of the data item inside an attribute on the listItem, so we know // which item it corresponds to. This will be useful later when we want to delete items listItem.setAttribute("data-note-id", cursor.value.id); // Create a button and place it inside each listItem const deleteBtn = document.createElement("button"); listItem.appendChild(deleteBtn); deleteBtn.textContent = "Delete"; // Set an event handler so that when the button is clicked, the deleteItem() // function is run deleteBtn.onclick = deleteItem; // Iterate to the next item in the cursor cursor.continue(); } else { // Again, if list item is empty, display a 'No notes stored' message if (!list.firstChild) { const listItem = document.createElement("li"); listItem.textContent = "No notes stored."; list.appendChild(listItem); } // if there are no more cursor items to iterate through, say so console.log("Notes all displayed"); } }; } </code></pre></div> <p>Again, let's break this down:</p> <ul> <li>First we empty out the <a href="/pt-BR/docs/Web/HTML/Element/ul"><code><ul></code></a> element's content, before then filling it with the updated content. If you didn't do this, you'd end up with a huge list of duplicated content being added to with each update.</li> <li>Next, we get a reference to the <code>notes_os</code> object store using <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/IDBDatabase/transaction"><code>IDBDatabase.transaction()</code></a> and <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/IDBTransaction/objectStore"><code>IDBTransaction.objectStore()</code></a> like we did in <code>addData()</code>, except here we are chaining them together in one line.</li> <li>The next step is to use <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/IDBObjectStore/openCursor"><code>IDBObjectStore.openCursor()</code></a> method to open a request for a cursor — this is a construct that can be used to iterate over the records in an object store. We chain an <code>onsuccess</code> handler on to the end of this line to make the code more concise — when the cursor is successfully returned, the handler is run.</li> <li>We get a reference to the cursor itself (an <a href="/pt-BR/docs/Web/API/IDBCursor"><code>IDBCursor</code></a> object) using let <code>cursor = e.target.result</code>.</li> <li>Next, we check to see if the cursor contains a record from the datastore (<code>if(cursor){ ... }</code>) — if so, we create a DOM fragment, populate it with the data from the record, and insert it into the page (inside the <code><ul></code> element). We also include a delete button that, when clicked, will delete that note by running the <code>deleteItem()</code> function, which we will look at in the next section.</li> <li>At the end of the <code>if</code> block, we use the <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/IDBCursor/continue"><code>IDBCursor.continue()</code></a> method to advance the cursor to the next record in the datastore, and run the content of the <code>if</code> block again. If there is another record to iterate to, this causes it to be inserted into the page, and then <code>continue()</code> is run again, and so on.</li> <li>When there are no more records to iterate over, <code>cursor</code> will return <code>undefined</code>, and therefore the <code>else</code> block will run instead of the <code>if</code> block. This block checks whether any notes were inserted into the <code><ul></code> — if not, it inserts a message to say no note was stored.</li> </ul></div></section><section aria-labelledby="deleting_a_note"><h3 id="deleting_a_note"><a href="#deleting_a_note">Deleting a note</a></h3><div class="section-content"><p>As stated above, when a note's delete button is pressed, the note is deleted. This is achieved by the <code>deleteItem()</code> function, which looks like so:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>// Define the deleteItem() function function deleteItem(e) { // retrieve the name of the task we want to delete. We need // to convert it to a number before trying it use it with IDB; IDB key // values are type-sensitive. let noteId = Number(e.target.parentNode.getAttribute("data-note-id")); // open a database transaction and delete the task, finding it using the id we retrieved above let transaction = db.transaction(["notes_os"], "readwrite"); let objectStore = transaction.objectStore("notes_os"); let request = objectStore.delete(noteId); // report that the data item has been deleted transaction.oncomplete = function () { // delete the parent of the button // which is the list item, so it is no longer displayed e.target.parentNode.parentNode.removeChild(e.target.parentNode); console.log("Note " + noteId + " deleted."); // Again, if list item is empty, display a 'No notes stored' message if (!list.firstChild) { let listItem = document.createElement("li"); listItem.textContent = "No notes stored."; list.appendChild(listItem); } }; } </code></pre></div> <ul> <li>The first part of this could use some explaining — we retrieve the ID of the record to be deleted using <code>Number(e.target.parentNode.getAttribute('data-note-id'))</code> — recall that the ID of the record was saved in a <code>data-note-id</code> attribute on the <code><li></code> when it was first displayed. We do however need to pass the attribute through the global built-in <a href="/pt-BR/docs/Web/JavaScript/Reference/Global_Objects/Number"><code>Number()</code></a> object as it is of datatype string, and therefore wouldn't be recognized by the database, which expects a number.</li> <li>We then get a reference to the object store using the same pattern we've seen previously, and use the <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/IDBObjectStore/delete"><code>IDBObjectStore.delete()</code></a> method to delete the record from the database, passing it the ID.</li> <li>When the database transaction is complete, we delete the note's <code><li></code> from the DOM, and again do the check to see if the <code><ul></code> is now empty, inserting a note as appropriate.</li> </ul> <p>So that's it! Your example should now work.</p> <p>If you are having trouble with it, feel free to <a href="https://mdn.github.io/learning-area/javascript/apis/client-side-storage/indexeddb/notes/" class="external" target="_blank">check it against our live example</a> (see the <a href="https://github.com/mdn/learning-area/blob/master/javascript/apis/client-side-storage/indexeddb/notes/index.js" class="external" target="_blank">source code</a> also).</p></div></section><section aria-labelledby="storing_complex_data_via_indexeddb"><h3 id="storing_complex_data_via_indexeddb"><a href="#storing_complex_data_via_indexeddb">Storing complex data via IndexedDB</a></h3><div class="section-content"><p>As we mentioned above, IndexedDB can be used to store more than just simple text strings. You can store just about anything you want, including complex objects such as video or image blobs. And it isn't much more difficult to achieve than any other type of data.</p> <p>To demonstrate how to do it, we've written another example called <a href="https://github.com/mdn/learning-area/tree/master/javascript/apis/client-side-storage/indexeddb/video-store" class="external" target="_blank">IndexedDB video store</a> (see it <a href="https://mdn.github.io/learning-area/javascript/apis/client-side-storage/indexeddb/video-store/" class="external" target="_blank">running live here also</a>). When you first run the example, it downloads all the videos from the network, stores them in an IndexedDB database, and then displays the videos in the UI inside <a href="/pt-BR/docs/Web/HTML/Element/video"><code><video></code></a> elements. The second time you run it, it finds the videos in the database and gets them from there instead before displaying them — this makes subsequent loads much quicker and less bandwidth-hungry.</p> <p>Let's walk through the most interesting parts of the example. We won't look at it all — a lot of it is similar to the previous example, and the code is well-commented.</p> <ol> <li> <p>For this simple example, we've stored the names of the videos to fetch in an array of objects:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>const videos = [ { name: "crystal" }, { name: "elf" }, { name: "frog" }, { name: "monster" }, { name: "pig" }, { name: "rabbit" }, ]; </code></pre></div> </li> <li> <p>To start with, once the database is successfully opened we run an <code>init()</code> function. This loops through the different video names, trying to load a record identified by each name from the <code>videos</code> database.</p> <p>If each video is found in the database (easily checked by seeing whether <code>request.result</code> evaluates to <code>true</code> — if the record is not present, it will be <code>undefined</code>), its video files (stored as blobs) and the video name are passed straight to the <code>displayVideo()</code> function to place them in the UI. If not, the video name is passed to the <code>fetchVideoFromNetwork()</code> function to ... you guessed it — fetch the video from the network.</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>function init() { // Loop through the video names one by one for (let i = 0; i < videos.length; i++) { // Open transaction, get object store, and get() each video by name let objectStore = db.transaction("videos_os").objectStore("videos_os"); let request = objectStore.get(videos[i].name); request.onsuccess = function () { // If the result exists in the database (is not undefined) if (request.result) { // Grab the videos from IDB and display them using displayVideo() console.log("taking videos from IDB"); displayVideo( request.result.mp4, request.result.webm, request.result.name, ); } else { // Fetch the videos from the network fetchVideoFromNetwork(videos[i]); } }; } } </code></pre></div> </li> <li> <p>The following snippet is taken from inside <code>fetchVideoFromNetwork()</code> — here we fetch MP4 and WebM versions of the video using two separate <a href="/pt-BR/docs/Web/API/Window/fetch" title="WindowOrWorkerGlobalScope.fetch()"><code>WindowOrWorkerGlobalScope.fetch()</code></a> requests. We then use the <a href="/pt-BR/docs/Web/API/Blob" title="Body.blob()"><code>Body.blob()</code></a> method to extract each response's body as a blob, giving us an object representation of the videos that can be stored and displayed later on.</p> <p>We have a problem here though — these two requests are both asynchronous, but we only want to try to display or store the video when both promises have fulfilled. Fortunately there is a built-in method that handles such a problem — <a href="/pt-BR/docs/Web/JavaScript/Reference/Global_Objects/Promise/all"><code>Promise.all()</code></a>. This takes one argument — references to all the individual promises you want to check for fulfillment placed in an array — and is itself promise-based.</p> <p>When all those promises have fulfilled, the <code>all()</code> promise fulfills with an array containing all the individual fulfillment values. Inside the <code>all()</code> block, you can see that we then call the <code>displayVideo()</code> function like we did before to display the videos in the UI, then we also call the <code>storeVideo()</code> function to store those videos inside the database.</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>let mp4Blob = fetch("videos/" + video.name + ".mp4").then((response) => response.blob(), ); let webmBlob = fetch("videos/" + video.name + ".webm").then((response) => response.blob(), ); // Only run the next code when both promises have fulfilled Promise.all([mp4Blob, webmBlob]).then(function (values) { // display the video fetched from the network with displayVideo() displayVideo(values[0], values[1], video.name); // store it in the IDB using storeVideo() storeVideo(values[0], values[1], video.name); }); </code></pre></div> </li> <li> <p>Let's look at <code>storeVideo()</code> first. This is very similar to the pattern you saw in the previous example for adding data to the database — we open a <code>readwrite</code> transaction and get a reference to our <code>videos_os</code> object store, create an object representing the record to add to the database, then simply add it using <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/IDBObjectStore/add"><code>IDBObjectStore.add()</code></a>.</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>function storeVideo(mp4Blob, webmBlob, name) { // Open transaction, get object store; make it a readwrite so we can write to the IDB let objectStore = db.transaction(['videos_os'], 'readwrite').objectStore('videos_os'); // Create a record to add to the IDB let record = { mp4 : mp4Blob, webm : webmBlob, name : name } // Add the record to the IDB using add() let request = objectStore.add(record); ... }; </code></pre></div> </li> <li> <p>Last but not least, we have <code>displayVideo()</code>, which creates the DOM elements needed to insert the video in the UI and then appends them to the page. The most interesting parts of this are those shown below — to actually display our video blobs in a <code><video></code> element, we need to create object URLs (internal URLs that point to the video blobs stored in memory) using the <a href="/pt-BR/docs/Web/API/URL/createObjectURL_static"><code>URL.createObjectURL()</code></a> method. Once that is done, we can set the object URLs to be the values of our <a href="/pt-BR/docs/Web/HTML/Element/source"><code><source></code></a> element's <code>src</code> attributes, and it works fine.</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>function displayVideo(mp4Blob, webmBlob, title) { // Create object URLs out of the blobs let mp4URL = URL.createObjectURL(mp4Blob); let webmURL = URL.createObjectURL(webmBlob); ... const video = document.createElement('video'); video.controls = true; const source1 = document.createElement('source'); source1.src = mp4URL; source1.type = 'video/mp4'; const source2 = document.createElement('source'); source2.src = webmURL; source2.type = 'video/webm'; ... } </code></pre></div> </li> </ol></div></section><section aria-labelledby="offline_asset_storage"><h2 id="offline_asset_storage"><a href="#offline_asset_storage">Offline asset storage</a></h2><div class="section-content"><p>The above example already shows how to create an app that will store large assets in an IndexedDB database, avoiding the need to download them more than once. This is already a great improvement to the user experience, but there is still one thing missing — the main HTML, CSS, and JavaScript files still need to be downloaded each time the site is accessed, meaning that it won't work when there is no network connection.</p> <p> <img src="/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs/Client-side_storage/ff-offline.png" alt="" width="765" height="307" loading="lazy"> </p> <p>This is where <a href="/pt-BR/docs/Web/API/Service_Worker_API">Service workers</a> and the closely-related <a href="/pt-BR/docs/Web/API/Cache">Cache API</a> come in.</p> <p>A service worker is a JavaScript file that, simply put, is registered against a particular origin (web site, or part of a web site at a certain domain) when it is accessed by a browser. When registered, it can control pages available at that origin. It does this by sitting between a loaded page and the network and intercepting network requests aimed at that origin.</p> <p>When it intercepts a request, it can do anything you wish to it (see <a href="/pt-BR/docs/Web/API/Service_Worker_API#other_use_case_ideas">use case ideas</a>), but the classic example is saving the network responses offline and then providing those in response to a request instead of the responses from the network. In effect, it allows you to make a web site work completely offline.</p> <p>The Cache API is a another client-side storage mechanism, with a bit of a difference — it is designed to save HTTP responses, and so works very well with service workers.</p> <div class="notecard note"> <p><strong>Nota:</strong> Service workers and Cache are supported in most modern browsers now. At the time of writing, Safari was still busy implementing it, but it should be there soon.</p> </div></div></section><section aria-labelledby="a_service_worker_example"><h3 id="a_service_worker_example"><a href="#a_service_worker_example">A service worker example</a></h3><div class="section-content"><p>Let's look at an example, to give you a bit of an idea of what this might look like. We have created another version of the video store example we saw in the previous section — this functions identically, except that it also saves the HTML, CSS, and JavaScript in the Cache API via a service worker, allowing the example to run offline!</p> <p>See <a href="https://mdn.github.io/learning-area/javascript/apis/client-side-storage/cache-sw/video-store-offline/" class="external" target="_blank">IndexedDB video store with service worker running live</a>, and also <a href="https://github.com/mdn/learning-area/tree/master/javascript/apis/client-side-storage/cache-sw/video-store-offline" class="external" target="_blank">see the source code</a>.</p> <h4 id="registering_the_service_worker">Registering the service worker</h4> <p>The first thing to note is that there's an extra bit of code placed in the main JavaScript file (see <a href="https://github.com/mdn/learning-area/blob/master/javascript/apis/client-side-storage/cache-sw/video-store-offline/index.js" class="external" target="_blank">index.js</a>). First we do a feature detection test to see if the <code>serviceWorker</code> member is available in the <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/Navigator"><code>Navigator</code></a> object. If this returns true, then we know that at least the basics of service workers are supported. Inside here we use the <a href="/pt-BR/docs/Web/API/ServiceWorkerContainer/register"><code>ServiceWorkerContainer.register()</code></a> method to register a service worker contained in the <code>sw.js</code> file against the origin it resides at, so it can control pages in the same directory as it, or subdirectories. When its promise fulfills, the service worker is deemed registered.</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>// Register service worker to control making site work offline if ("serviceWorker" in navigator) { navigator.serviceWorker .register( "/learning-area/javascript/apis/client-side-storage/cache-sw/video-store-offline/sw.js", ) .then(function () { console.log("Service Worker Registered"); }); } </code></pre></div> <div class="notecard note"> <p><strong>Nota:</strong> The given path to the <code>sw.js</code> file is relative to the site origin, not the JavaScript file that contains the code. The service worker is at <code>https://mdn.github.io/learning-area/javascript/apis/client-side-storage/cache-sw/video-store-offline/sw.js</code>. The origin is <code>https://mdn.github.io</code>, and therefore the given path has to be <code>/learning-area/javascript/apis/client-side-storage/cache-sw/video-store-offline/sw.js</code>. If you wanted to host this example on your own server, you'd have to change this accordingly. This is rather confusing, but it has to work this way for security reasons.</p> </div> <h4 id="installing_the_service_worker">Installing the service worker</h4> <p>The next time any page under the service worker's control is accessed (e.g. when the example is reloaded), the service worker is installed against that page, meaning that it will start controlling it. When this occurs, an <code>install</code> event is fired against the service worker; you can write code inside the service worker itself that will respond to the installation.</p> <p>Let's look at an example, in the <a href="https://github.com/mdn/learning-area/blob/master/javascript/apis/client-side-storage/cache-sw/video-store-offline/sw.js" class="external" target="_blank">sw.js</a> file (the service worker). You'll see that the install listener is registered against <code>self</code>. This <code>self</code> keyword is a way to refer to the global scope of the service worker from inside the service worker file.</p> <p>Inside the <code>install</code> handler we use the <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/ExtendableEvent/waitUntil"><code>ExtendableEvent.waitUntil()</code></a> method, available on the event object, to signal that the browser shouldn't complete installation of the service worker until after the promise inside it has fulfilled successfully.</p> <p>Here is where we see the Cache API in action. We use the <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/CacheStorage/open"><code>CacheStorage.open()</code></a> method to open a new cache object in which responses can be stored (similar to an IndexedDB object store). This promise fulfills with a <a href="/pt-BR/docs/Web/API/Cache"><code>Cache</code></a> object representing the <code>video-store</code> cache. We then use the <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/Cache/addAll"><code>Cache.addAll()</code></a> method to fetch a series of assets and add their responses to the cache.</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>self.addEventListener("install", function (e) { e.waitUntil( caches.open("video-store").then(function (cache) { return cache.addAll([ "/learning-area/javascript/apis/client-side-storage/cache-sw/video-store-offline/", "/learning-area/javascript/apis/client-side-storage/cache-sw/video-store-offline/index.html", "/learning-area/javascript/apis/client-side-storage/cache-sw/video-store-offline/index.js", "/learning-area/javascript/apis/client-side-storage/cache-sw/video-store-offline/style.css", ]); }), ); }); </code></pre></div> <p>That's it for now, installation done.</p> <h4 id="responding_to_further_requests">Responding to further requests</h4> <p>With the service worker registered and installed against our HTML page, and the relevant assets all added to our cache, we are nearly ready to go. There is only one more thing to do, write some code to respond to further network requests.</p> <p>This is what the second bit of code in <code>sw.js</code> does. We add another listener to the service worker global scope, which runs the handler function when the <code>fetch</code> event is raised. This happens whenever the browser makes a request for an asset in the directory the service worker is registered against.</p> <p>Inside the handler we first log the URL of the requested asset. We then provide a custom response to the request, using the <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/FetchEvent/respondWith"><code>FetchEvent.respondWith()</code></a> method.</p> <p>Inside this block we use <a class="only-in-en-us" title="Esta página está disponível apenas em inglês no momento" href="/en-US/docs/Web/API/CacheStorage/match"><code>CacheStorage.match()</code></a> to check whether a matching request (i.e. matches the URL) can be found in any cache. This promise fulfills with the matching response if a match is found, or <code>undefined</code> if it isn't.</p> <p>If a match is found, we simply return it as the custom response. If not, we <a href="/pt-BR/docs/Web/API/Window/fetch">fetch()</a> the response from the network and return that instead.</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>self.addEventListener("fetch", function (e) { console.log(e.request.url); e.respondWith( caches.match(e.request).then(function (response) { return response || fetch(e.request); }), ); }); </code></pre></div> <p>And that is it for our simple service worker. There is a whole load more you can do with them — for a lot more detail, see the <a href="https://github.com/mdn/serviceworker-cookbook/" class="external" target="_blank">service worker cookbook</a>. And thanks to Paul Kinlan for his article <a href="https://developers.google.com/web/fundamentals/codelabs/offline/" class="external" target="_blank">Adding a Service Worker and Offline into your Web App</a>, which inspired this simple example.</p> <h4 id="testing_the_example_offline">Testing the example offline</h4> <p>To test our <a href="https://mdn.github.io/learning-area/javascript/apis/client-side-storage/cache-sw/video-store-offline/" class="external" target="_blank">service worker example</a>, you'll need to load it a couple of times to make sure it is installed. Once this is done, you can:</p> <ul> <li>Try unplugging your network/turning your Wifi off.</li> <li>Select <em>File > Work Offline</em> if you are using Firefox.</li> <li>Go to the devtools, then choose <em>Application > Service Workers</em>, then check the <em>Offline</em> checkbox if you are using Chrome.</li> </ul> <p>If you refresh your example page again, you should still see it load just fine. Everything is stored offline — the page assets in a cache, and the videos in an IndexedDB database.</p></div></section><section aria-labelledby="summary"><h2 id="summary"><a href="#summary">Summary</a></h2><div class="section-content"><p>That's it for now. We hope you've found our rundown of client-side storage technologies useful.</p></div></section><section aria-labelledby="see_also"><h2 id="see_also"><a href="#see_also">See also</a></h2><div class="section-content"><ul> <li><a href="/pt-BR/docs/Web/API/Web_Storage_API">Web storage API</a></li> <li><a href="/pt-BR/docs/Web/API/IndexedDB_API">IndexedDB API</a></li> <li><a href="/pt-BR/docs/Web/HTTP/Cookies">Cookies</a></li> <li><a href="/pt-BR/docs/Web/API/Service_Worker_API">Service worker API</a></li> </ul><ul class="prev-next"> <li><a class="button secondary only-in-en-us" href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Video_and_audio_APIs" title="Esta página está disponível apenas em inglês no momento"><span class="button-wrap"> Anterior </span></a></li> <li><a class="button secondary" href="/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs"><span class="button-wrap"> Menu: APIs web do lado cliente</span></a></li> </ul></div></section></article><aside 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href=\"/pt-BR/docs/Learn/CSS/First_steps/What_is_CSS\">O que é CSS?</a></li><li><a href=\"/pt-BR/docs/Learn/CSS/First_steps/Getting_started\">Iniciando com CSS</a></li><li><a href=\"/pt-BR/docs/Learn/CSS/First_steps/How_CSS_is_structured\">Como CSS é estruturado</a></li><li><a href=\"/pt-BR/docs/Learn/CSS/First_steps/How_CSS_works\">Como funciona o CSS</a></li><li><a href=\"/pt-BR/docs/Learn/CSS/First_steps/Styling_a_biography_page\">Usando seu novo conhecimento</a></li></ol></details></li><li><details><summary>CSS building blocks</summary><ol><li><a href=\"/pt-BR/docs/Learn/CSS/Building_blocks\">Construindo blocos CSS</a></li><li><a href=\"/pt-BR/docs/Learn/CSS/Building_blocks/Selectors\">CSS selectors</a></li><li><a href=\"/pt-BR/docs/Learn/CSS/Building_blocks/Selectors/Type_Class_and_ID_Selectors\">Seletores de tipo, classe e ID</a></li><li><a href=\"/pt-BR/docs/Learn/CSS/Building_blocks/Selectors/Attribute_selectors\">Seletores de atributo</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Building_blocks/Selectors/Pseudo-classes_and_pseudo-elements\">Pseudo-classes and pseudo-elements</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Building_blocks/Selectors/Combinators\">Combinators</a></li><li><a href=\"/pt-BR/docs/Learn/CSS/Building_blocks/Cascade_and_inheritance\">Cascata, especificidade e herança</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Building_blocks/Cascade_layers\">Cascade layers</a></li><li><a href=\"/pt-BR/docs/Learn/CSS/Building_blocks/The_box_model\">The box model</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Building_blocks/Backgrounds_and_borders\">Backgrounds and borders</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Building_blocks/Handling_different_text_directions\">Handling different text directions</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Building_blocks/Overflowing_content\">Overflowing content</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Building_blocks/Values_and_units\">CSS values and units</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Building_blocks/Sizing_items_in_CSS\">Sizing items in CSS</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Building_blocks/Images_media_form_elements\">Images, media, and form elements</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Building_blocks/Styling_tables\">Styling tables</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Building_blocks/Advanced_styling_effects\">Advanced styling effects</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Building_blocks/Debugging_CSS\">Debugging CSS</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Building_blocks/Organizing\">Organizing your CSS</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Building_blocks/Fundamental_CSS_comprehension\">Fundamental CSS comprehension</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Building_blocks/Creating_fancy_letterheaded_paper\">Creating fancy letterheaded paper</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Building_blocks/A_cool_looking_box\">A cool-looking box</a></li></ol></details></li><li><details><summary>Estilização de textos</summary><ol><li><a href=\"/pt-BR/docs/Learn/CSS/Styling_text\">Estilizando texto</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Styling_text/Fundamentals\">Fundamental text and font styling</a></li><li><a href=\"/pt-BR/docs/Learn/CSS/Styling_text/Styling_lists\">Manipulando Listas</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Styling_text/Styling_links\">Styling links</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Styling_text/Web_fonts\">Web fonts</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Styling_text/Typesetting_a_homepage\">Typesetting a community school homepage</a></li></ol></details></li><li><details><summary>Esquemas CSS</summary><ol><li><a href=\"/pt-BR/docs/Learn/CSS/CSS_layout\">CSS layout</a></li><li><a href=\"/pt-BR/docs/Learn/CSS/CSS_layout/Introduction\">Introdução ao leiaute com CSS</a></li><li><a href=\"/pt-BR/docs/Learn/CSS/CSS_layout/Normal_Flow\">Fluxo Normal</a></li><li><a href=\"/pt-BR/docs/Learn/CSS/CSS_layout/Flexbox\">Flexbox</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/CSS_layout/Grids\">Grids</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/CSS_layout/Floats\">Floats</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/CSS_layout/Positioning\">Positioning</a></li><li><a href=\"/pt-BR/docs/Learn/CSS/CSS_layout/Multiple-column_Layout\">Layout de varias colunas</a></li><li><a href=\"/pt-BR/docs/Learn/CSS/CSS_layout/Responsive_Design\">Design Responsivo</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/CSS_layout/Media_queries\">Beginner's guide to media queries</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/CSS_layout/Legacy_Layout_Methods\">Legacy layout methods</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/CSS_layout/Supporting_Older_Browsers\">Supporting older browsers</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/CSS_layout/Fundamental_Layout_Comprehension\">Fundamental layout comprehension</a></li></ol></details></li><li class=\"section\"><a href=\"/pt-BR/docs/Learn/JavaScript\">JavaScript — Uma linguagem de script dinâmica para aplicações cliente</a></li><li><details><summary>Primeiros passos com JavaScript</summary><ol><li><a href=\"/pt-BR/docs/Learn/JavaScript/First_steps\">Primeiros passos com JavaScript</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/First_steps/What_is_JavaScript\">O que é JavaScript?</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/First_steps/A_first_splash\">Um primeiro mergulho no JavaScript</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/First_steps/What_went_wrong\">O que deu errado? Resolvendo problemas no JavaScript</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/First_steps/Variables\">Armazenando as informações que você precisa — Variáveis</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/First_steps/Math\">Matemática básica no JavaScript — números e operadores</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/First_steps/Strings\">Trabalhando com texto — strings em JavaScript</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/First_steps/Useful_string_methods\">Métodos úteis de string</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/First_steps/Arrays\">Arrays</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/First_steps/Silly_story_generator\">Gerador de histórias bobas</a></li></ol></details></li><li><details><summary>Programando em JavaScript</summary><ol><li><a href=\"/pt-BR/docs/Learn/JavaScript/Building_blocks\">Elementos construtivos do Javascript</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/Building_blocks/conditionals\">Tomando decisões no seu código — condicionais</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/Building_blocks/Looping_code\">Código em loop</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/Building_blocks/Functions\">Funções — blocos reutilizáveis de código</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/Building_blocks/Build_your_own_function\">Construa sua própria função</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/Building_blocks/Return_values\">Valores de retorno de função</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/Building_blocks/Events\">Introdução a eventos</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/Building_blocks/Event_bubbling\">Comparativo entre Event Targets</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/Building_blocks/Image_gallery\">Galeria de Imagens</a></li></ol></details></li><li><details><summary>Introdução Objetos em JavaScript</summary><ol><li><a href=\"/pt-BR/docs/Learn/JavaScript/Objects\">Introdução a objetos em Javascript</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/Objects/Basics\">O básico sobre objetos JavaScript</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/Objects/Object_prototypes\">Protótipos de objetos</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/JavaScript/Objects/Object-oriented_programming\">Object-oriented programming</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/Objects/Classes_in_JavaScript\">Herança em JavaScript</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/Objects/JSON\">Trabalhando com JSON</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/Objects/Object_building_practice\">Prática de construção de objetos</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/Objects/Adding_bouncing_balls_features\">Adicionando recursos à nossa demonstração de bolas pulantes</a></li></ol></details></li><li><details><summary>Asynchronous JavaScript</summary><ol><li><a href=\"/pt-BR/docs/Learn/JavaScript/Asynchronous\">JavaScript Assíncrono</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/Asynchronous/Introducing\">Introdução ao JavaScript Async</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/Asynchronous/Promises\">Como usar Promises</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/JavaScript/Asynchronous/Implementing_a_promise-based_API\">How to implement a promise-based API</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/JavaScript/Asynchronous/Introducing_workers\">Introducing workers</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/JavaScript/Asynchronous/Sequencing_animations\">Sequencing animations</a></li></ol></details></li><li><details open=\"\"><summary>APIs Web na aplicação Cliente</summary><ol><li><a href=\"/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs\">APIs web do lado cliente</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs/Introduction\">Introdução às Web APIs</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs/Manipulating_documents\">JavaScript e CSS</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs/Fetching_data\">AJAX</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Third_party_APIs\">Third-party APIs</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Drawing_graphics\">Drawing graphics</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Video_and_audio_APIs\">Video and Audio APIs</a></li><li><em><a href=\"/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs/Client-side_storage\" aria-current=\"page\">Client-side storage</a></em></li></ol></details></li><li class=\"section\"><a href=\"/pt-BR/docs/Learn/Forms\">Web forms — Working with user data</a></li><li><details><summary>Web form building blocks</summary><ol><li><a href=\"/pt-BR/docs/Learn/Forms\">Formulários da Web - Trabalhando com dados do usuário</a></li><li><a href=\"/pt-BR/docs/Learn/Forms/Your_first_form\">Meu primeiro formulário HTML</a></li><li><a href=\"/pt-BR/docs/Learn/Forms/How_to_structure_a_web_form\">Como estruturar um formulário HTML</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Forms/Basic_native_form_controls\">Basic native form controls</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Forms/HTML5_input_types\">The HTML5 input types</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Forms/Other_form_controls\">Other form controls</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Forms/Styling_web_forms\">Styling web forms</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Forms/Advanced_form_styling\">Advanced form styling</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Forms/UI_pseudo-classes\">UI pseudo-classes</a></li><li><a href=\"/pt-BR/docs/Learn/Forms/Form_validation\">Form data validation</a></li><li><a href=\"/pt-BR/docs/Learn/Forms/Sending_and_retrieving_form_data\">Sending form data</a></li></ol></details></li><li><details><summary>Advanced web form techniques</summary><ol><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Forms/How_to_build_custom_form_controls\">How to build custom form controls</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Forms/Sending_forms_through_JavaScript\">Sending forms through JavaScript</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Forms/Property_compatibility_table_for_form_controls\">CSS property compatibility table for form controls</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Forms/HTML_forms_in_legacy_browsers\">HTML forms in legacy browsers</a></li></ol></details></li><li class=\"section\"><a href=\"/pt-BR/docs/Learn/Accessibility\">Acessibilidade — Faça a Internet usável por qualquer pessoa</a></li><li><details><summary>Guias de acessibilidade</summary><ol><li><a href=\"/pt-BR/docs/Learn/Accessibility\">Accessibility</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Accessibility/What_is_accessibility\">What is accessibility?</a></li><li><a href=\"/pt-BR/docs/Learn/Accessibility/HTML\">HTML: Boas práticas em acessibilidade</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Accessibility/CSS_and_JavaScript\">CSS and JavaScript accessibility best practices</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Accessibility/WAI-ARIA_basics\">WAI-ARIA basics</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Accessibility/Multimedia\">Accessible multimedia</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Accessibility/Mobile\">Mobile accessibility</a></li><li><a href=\"/pt-BR/docs/Learn/Accessibility/Accessibility_troubleshooting\">Avaliação: solucionando problemas de acessibilidade</a></li></ol></details></li><li class=\"section\"><a href=\"/pt-BR/docs/Learn/Performance\">Performance — Making websites fast and responsive</a></li><li><details><summary>Performance guides</summary><ol><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Performance\">Web performance</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Performance/why_web_performance\">The \"why\" of web performance</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Performance/What_is_web_performance\">What is web performance?</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Performance/Perceived_performance\">Perceived performance</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Performance/Measuring_performance\">Measuring performance</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Performance/Multimedia\">Multimedia: Images</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Performance/video\">Multimedia: video</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Performance/JavaScript\">JavaScript performance optimization</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Performance/HTML\">HTML performance optimization</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Performance/CSS\">CSS performance optimization</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Performance/business_case_for_performance\">The business case for web performance</a></li></ol></details></li><li class=\"section\"><a href=\"/pt-BR/docs/Learn/MathML\">MathML — Writing mathematics with MathML</a></li><li><details><summary>MathML first steps</summary><ol><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/MathML/First_steps\">MathML first steps</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/MathML/First_steps/Getting_started\">Getting started with MathML</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/MathML/First_steps/Text_containers\">MathML Text Containers</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/MathML/First_steps/Fractions_and_roots\">MathML fractions and roots</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/MathML/First_steps/Scripts\">MathML scripted elements</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/MathML/First_steps/Tables\">MathML tables</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/MathML/First_steps/Three_famous_mathematical_formulas\">Three famous mathematical formulas</a></li></ol></details></li><li class=\"section\"><a href=\"/pt-BR/docs/Learn/../Games\">Games — Developing games for the web</a></li><li><details><summary>Guides and tutorials</summary><ol><li><a href=\"/pt-BR/docs/Games/Introduction\">Introdução ao desenvolvimento de jogos para a Web</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Games/Techniques\">Techniques for game development</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Games/Tutorials\">Tutorials</a></li><li><a href=\"/pt-BR/docs/Games/Publishing_games\">Publishing games</a></li></ol></details></li><li class=\"section\"><a href=\"/pt-BR/docs/Learn/Tools_and_testing\">Ferramentas e teste</a></li><li><details><summary>Client-side web development tools</summary><ol><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools\">Understanding client-side web development tools</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Overview\">Client-side tooling overview</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Command_line\">Command line crash course</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Package_management\">Package management basics</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Introducing_complete_toolchain\">Introducing a complete toolchain</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Deployment\">Deploying our app</a></li></ol></details></li><li><details><summary>Introduction to client-side frameworks</summary><ol><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Introduction\">Introduction to client-side frameworks</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Main_features\">Framework main features</a></li></ol></details></li><li><details><summary>React</summary><ol><li><a href=\"/pt-BR/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_getting_started\">Começando com React</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_todo_list_beginning\">Beginning our React todo list</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_components\">Componentizing our React app</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_interactivity_events_state\">React interactivity: Events and state</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_interactivity_filtering_conditional_rendering\">React interactivity: Editing, filtering, conditional rendering</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_accessibility\">Accessibility in React</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_resources\">React resources</a></li></ol></details></li><li><details><summary>Ember</summary><ol><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_getting_started\">Getting started with Ember</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_structure_componentization\">Ember app structure and componentization</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_interactivity_events_state\">Ember interactivity: Events, classes and state</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_conditional_footer\">Ember Interactivity: Footer functionality, conditional rendering</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_routing\">Routing in Ember</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_resources\">Ember resources and troubleshooting</a></li></ol></details></li><li><details><summary>Vue</summary><ol><li><a href=\"/pt-BR/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_getting_started\">Iniciando com Vue</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_first_component\">Creating our first Vue component</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_rendering_lists\">Rendering a list of Vue components</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_methods_events_models\">Adding a new todo form: Vue events, methods, and models</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_styling\">Styling Vue components with CSS</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_computed_properties\">Using Vue computed properties</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_conditional_rendering\">Vue conditional rendering: editing existing todos</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_refs_focus_management\">Vue refs and lifecycle methods for focus management</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_resources\">Vue resources</a></li></ol></details></li><li><details><summary>Svelte</summary><ol><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_getting_started\">Getting started with Svelte</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_Todo_list_beginning\">Starting our Svelte to-do list app</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_variables_props\">Dynamic behavior in Svelte: working with variables and props</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_components\">Componentizing our Svelte app</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_reactivity_lifecycle_accessibility\">Advanced Svelte: Reactivity, lifecycle, accessibility</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_stores\">Working with Svelte stores</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_TypeScript\">TypeScript support in Svelte</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_deployment_next\">Deployment and next steps</a></li></ol></details></li><li><details><summary>Angular</summary><ol><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_getting_started\">Getting started with Angular</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_todo_list_beginning\">Beginning our Angular todo list app</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_styling\">Styling our Angular app</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_item_component\">Creating an item component</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_filtering\">Filtering our to-do items</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_building\">Building Angular applications and further resources</a></li></ol></details></li><li><details><summary>Git and GitHub</summary><ol><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/GitHub\">Git and GitHub</a></li></ol></details></li><li><details><summary>Testes entre navegadores</summary><ol><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing\">Cross browser testing</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Introduction\">Introduction to cross-browser testing</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Testing_strategies\">Strategies for carrying out testing</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/HTML_and_CSS\">Handling common HTML and CSS problems</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/JavaScript\">Handling common JavaScript problems</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Accessibility\">Handling common accessibility problems</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Feature_detection\">Implementing feature detection</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Automated_testing\">Introduction to automated testing</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Your_own_automation_environment\">Setting up your own test automation environment</a></li></ol></details></li><li class=\"section\"><a href=\"/pt-BR/docs/Learn/Server-side\">Programação de servidores de Aplicação</a></li><li><details><summary>Primeiros passos</summary><ol><li><a href=\"/pt-BR/docs/Learn/Server-side/First_steps\">Primeiros passos programando o site no servidor</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/First_steps/Introduction\">Introdução ao lado servidor</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/First_steps/Client-Server_overview\">Visão geral do cliente-servidor</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Server-side/First_steps/Web_frameworks\">Server-side web frameworks</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/First_steps/Website_security\">Segurança em aplicação web</a></li></ol></details></li><li><details><summary>Framework Web Django (Python)</summary><ol><li><a href=\"/pt-BR/docs/Learn/Server-side/Django\">Django Web Framework (Python)</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/Django/Introduction\">Introdução ao Django</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/Django/development_environment\">Configurando um ambiente de desenvolvimento Django</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/Django/Tutorial_local_library_website\">Tutorial Django: Website da Biblioteca Local</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/Django/skeleton_website\">Django Tutorial Parte 2: Criando o \"esqueleto\" de um site</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/Django/Models\">Tutorial Django Parte 3: Usando models</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/Django/Admin_site\">Tutorial Django Parte 4: Django admin site</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/Django/Home_page\">Django Tutorial Parte 5: Criando nossa home page</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/Django/Generic_views\">Tutorial Django Parte 6: Lista genérica e detail views</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/Django/Sessions\">Tutorial Django Parte 7: Sessões</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/Django/Authentication\">Tutorial Django Parte 8: Autenticação de usuário e permissões</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/Django/Forms\">Tutorial Django Parte 9: Trabalhando com formulários</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/Django/Testing\">Tutorial Django Parte 10: Testando uma aplicação web Django</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/Django/Deployment\">Tutorial Django Parte 11: Hospedando Django para produção</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/Django/web_application_security\">Segurança de aplicações web Django</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Server-side/Django/django_assessment_blog\">Assessment: DIY Django mini blog</a></li></ol></details></li><li><details><summary>Framework Web Express (Node.js/JavaScript)</summary><ol><li><a href=\"/pt-BR/docs/Learn/Server-side/Express_Nodejs\">Express Web Framework (Node.js/JavaScript)</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/Express_Nodejs/Introduction\">Introdução Express/Node</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/Express_Nodejs/development_environment\">Configurando o Node como ambiente de desenvolvimento</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/Express_Nodejs/Tutorial_local_library_website\">Express: Tutorial para criar o site de uma Biblioteca Local</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/Express_Nodejs/skeleton_website\">Express Tutorial Parte 2: Criando a estrutura do website</a></li><li><a href=\"/pt-BR/docs/Learn/Server-side/Express_Nodejs/mongoose\">Tutorial Express Parte 3: Usando um banco de dados (com Mongoose)</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/routes\">Express Tutorial Part 4: Routes and controllers</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/Displaying_data\">Express Tutorial Part 5: Displaying library data</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/forms\">Express Tutorial Part 6: Working with forms</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/deployment\">Express Tutorial Part 7: Deploying to production</a></li></ol></details></li><li class=\"section\"><a href=\"/pt-BR/docs/Learn/Common_questions\">Mais recursos</a></li><li><details><summary>Questões gerais</summary><ol><li><a href=\"/pt-BR/docs/Learn/Common_questions\">Questões comuns</a></li><li><a href=\"/pt-BR/docs/Learn/HTML/Howto\">Use HTML para resolver problemas comuns</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/CSS/Howto\">Use CSS to solve common problems</a></li><li><a href=\"/pt-BR/docs/Learn/JavaScript/Howto\">Solve common problems in your JavaScript code</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Common_questions/Web_mechanics\">Web mechanics</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Common_questions/Tools_and_setup\">Tools and setup</a></li><li><a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Learn/Common_questions/Design_and_accessibility\">Design and accessibility</a></li></ol></details></li></ol>","sidebarMacro":"LearnSidebar","body":[{"type":"prose","value":{"id":null,"title":null,"isH3":false,"content":"<ul class=\"prev-next\">\n <li><a class=\"button secondary only-in-en-us\" href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Video_and_audio_APIs\" title=\"Esta página está disponível apenas em inglês no momento\"><span class=\"button-wrap\"> Anterior </span></a></li>\n <li><a class=\"button secondary\" href=\"/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs\"><span class=\"button-wrap\"> Menu: APIs web do lado cliente</span></a></li>\n \n</ul>\n<p>Os navegadores modernos oferecem suporte a várias maneiras de os sites armazenarem dados no computador do usuário - com a permissão do usuário - e depois recuperá-los quando necessário. Isso permite que você mantenha dados para armazenamento de longo prazo, salve sites ou documentos para uso offline, retenha configurações específicas do usuário para seu site e muito mais. Este artigo explica os princípios básicos de como eles funcionam.</p>\n<figure class=\"table-container\"><table class=\"learn-box standard-table\">\n <tbody>\n <tr>\n <th scope=\"row\">Pré-requisitos:</th>\n <td>\n Noções básicas de JavaScript (consulte as\n <a href=\"/pt-BR/docs/Learn/JavaScript/First_steps\">primeiras etapas </a><a href=\"/pt-BR/docs/Learn/JavaScript/First_steps\"></a>,\n <a href=\"/pt-BR/docs/Learn/JavaScript/Building_blocks\">blocos de construção</a>\n ,\n <a href=\"/pt-BR/docs/Learn/JavaScript/Objects\">objetos JavaScript</a> ),\n as\n <a href=\"/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs/Introduction\">noções básicas de APIs do lado do cliente</a>\n </td>\n </tr>\n <tr>\n <th scope=\"row\">Objetivo:</th>\n <td>\n Para aprender como usar APIs de armazenamento do lado do cliente para\n armazenar dados de aplicativos\n </td>\n </tr>\n </tbody>\n</table></figure>"}},{"type":"prose","value":{"id":"armazenamento_do_lado_do_cliente","title":"Armazenamento do lado do cliente?","isH3":false,"content":"<p>Em outro lugar na área de aprendizagem MDN, falamos sobre a diferença entre <a href=\"/pt-BR/docs/Learn/Server-side/First_steps/Client-Server_overview#static_sites\">sites estáticos</a> e <a href=\"/pt-BR/docs/Learn/Server-side/First_steps/Client-Server_overview#dynamic_sites\">sites dinâmicos</a> . A maioria dos principais sites modernos são dinâmicos - eles armazenam dados no servidor usando algum tipo de banco de dados (armazenamento do lado do servidor) e, em seguida, executam o código do <a href=\"/pt-BR/docs/Learn/Server-side\">lado do servidor</a> para recuperar os dados necessários, inserem-nos em modelos de página estática e fornecem o HTML resultante para o cliente a ser exibido pelo navegador do usuário.er.</p>\n<p>O armazenamento do lado do cliente funciona em princípios semelhantes, mas tem usos diferentes. Consiste em APIs JavaScript que permitem armazenar dados no cliente (ou seja, na máquina do usuário) e recuperá-los quando necessário. Isso tem muitos usos distintos, como:</p>\n<ul>\n <li>Personalizar as preferências do site (por exemplo, mostrar a escolha do usuário de widgets personalizados, esquema de cores ou tamanho da fonte).</li>\n <li>Atividade anterior persistente do site (por exemplo, armazenar o conteúdo de um carrinho de compras de uma sessão anterior, lembrando se um usuário estava conectado anteriormente).</li>\n <li>Salvar dados e ativos localmente para que o download de um site seja mais rápido (e potencialmente mais barato) ou possa ser usado sem uma conexão de rede.</li>\n <li>Salvar documentos gerados por aplicativos da web localmente para uso offline</li>\n</ul>\n<p>Freqüentemente, o armazenamento do lado do cliente e do lado do servidor são usados juntos. Por exemplo, você pode baixar um lote de arquivos de música (talvez usados por um jogo da web ou aplicativo de reprodutor de música), armazená-los em um banco de dados do cliente e reproduzi-los conforme necessário. O usuário só teria que baixar os arquivos de música uma vez - em visitas subsequentes, eles seriam recuperados do banco de dados.</p>\n<div class=\"notecard note\">\n <p><strong>Nota:</strong> : Existem limites para a quantidade de dados que você pode armazenar usando APIs de armazenamento do lado do cliente (possivelmente por API individual e cumulativamente); o limite exato varia dependendo do navegador e, possivelmente, com base nas configurações do usuário. Consulte <a href=\"/en-US/docs/Web/API/Storage_API/Storage_quotas_and_eviction_criteria\" class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\">Limites de armazenamento do navegador e critérios de despejo</a> para obter mais informações..</p>\n</div>"}},{"type":"prose","value":{"id":"old_school_cookies","title":"Old school: Cookies","isH3":true,"content":"<p>The concept of client-side storage has been around for <strong>Nota</strong> : Existem limites para a quantidade de dados que você pode armazenar usando APIs de armazenamento do lado do cliente (possivelmente por API individual e cumulativamente); o limite exato varia dependendo do navegador e, possivelmente, com base nas configurações do usuário. Consultea long time. Since the early days of the web, sites have used <a href=\"/pt-BR/docs/Web/HTTP/Cookies\">cookies</a> to store information to personalize user experience on websites. They're the earliest form of client-side storage commonly used on the web.</p>\n<p>These days, there are easier mechanisms available for storing client-side data, therefore we won't be teaching you how to use cookies in this article. However, this does not mean cookies are completely useless on the modern-day web — they are still used commonly to store data related to user personalization and state, e.g. session IDs and access tokens. For more information on cookies see our <a href=\"/pt-BR/docs/Web/HTTP/Cookies\">Using HTTP cookies</a> article.</p>"}},{"type":"prose","value":{"id":"new_school_web_storage_and_indexeddb","title":"New school: Web Storage and IndexedDB","isH3":true,"content":"<p>The \"easier\" features we mentioned above are as follows:</p>\n<ul>\n <li>The <a href=\"/pt-BR/docs/Web/API/Web_Storage_API\">Web Storage API</a> provides a very simple syntax for storing and retrieving smaller, data items consisting of a name and a corresponding value. This is useful when you just need to store some simple data, like the user's name, whether they are logged in, what color to use for the background of the screen, etc.</li>\n <li>The <a href=\"/pt-BR/docs/Web/API/IndexedDB_API\">IndexedDB API</a> provides the browser with a complete database system for storing complex data. This can be used for things from complete sets of customer records to even complex data types like audio or video files.</li>\n</ul>\n<p>You'll learn more about these APIs below.</p>"}},{"type":"prose","value":{"id":"the_future_cache_api","title":"The future: Cache API","isH3":true,"content":"<p>Some modern browsers support the new <a href=\"/pt-BR/docs/Web/API/Cache\"><code>Cache</code></a> API. This API is designed for storing HTTP responses to specific requests, and is very useful for doing things like storing website assets offline so the site can subsequently be used without a network connection. Cache is usually used in combination with the <a href=\"/pt-BR/docs/Web/API/Service_Worker_API\">Service Worker API</a>, although it doesn't have to be.</p>\n<p>Use of Cache and Service Workers is an advanced topic, and we won't be covering it in great detail in this article, although we will show a simple example in the <a href=\"#offline_asset_storage\">Offline asset storage</a> section below.</p>"}},{"type":"prose","value":{"id":"storing_simple_data_—_web_storage","title":"Storing simple data — web storage","isH3":false,"content":"<p>The <a href=\"/pt-BR/docs/Web/API/Web_Storage_API\">Web Storage API</a> is very easy to use — you store simple name/value pairs of data (limited to strings, numbers, etc.) and retrieve these values when needed.</p>"}},{"type":"prose","value":{"id":"basic_syntax","title":"Basic syntax","isH3":true,"content":"<p>Let's show you how:</p>\n<ol>\n <li>\n <p>First, go to our <a href=\"https://mdn.github.io/learning-area/javascript/apis/client-side-storage/web-storage/index.html\" class=\"external\" target=\"_blank\">web storage blank template</a> on GitHub (open this in a new tab).</p>\n </li>\n <li>\n <p>Open the JavaScript console of your browser's developer tools.</p>\n </li>\n <li>\n <p>All of your web storage data is contained within two object-like structures inside the browser: <a href=\"/pt-BR/docs/Web/API/Window/sessionStorage\" title=\"sessionStorage\"><code>sessionStorage</code></a> and <a href=\"/pt-BR/docs/Web/API/Window/localStorage\" title=\"localStorage\"><code>localStorage</code></a>. The first one persists data for as long as the browser is open (the data is lost when the browser is closed) and the second one persists data even after the browser is closed and then opened again. We'll use the second one in this article as it is generally more useful.</p>\n <p>The <a href=\"/pt-BR/docs/Web/API/Storage/setItem\"><code>Storage.setItem()</code></a> method allows you to save a data item in storage — it takes two parameters: the name of the item, and its value. Try typing this into your JavaScript console (change the value to your own name, if you wish!):</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>localStorage.setItem(\"name\", \"Chris\");\n</code></pre></div>\n </li>\n <li>\n <p>The <a href=\"/pt-BR/docs/Web/API/Storage/getItem\"><code>Storage.getItem()</code></a> method takes one parameter — the name of a data item you want to retrieve — and returns the item's value. Now type these lines into your JavaScript console:</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>let myName = localStorage.getItem(\"name\");\nmyName;\n</code></pre></div>\n <p>Upon typing in the second line, you should see that the <code>myName</code> variable now contains the value of the <code>name</code> data item.</p>\n </li>\n <li>\n <p>The <a href=\"/pt-BR/docs/Web/API/Storage/removeItem\"><code>Storage.removeItem()</code></a> method takes one parameter — the name of a data item you want to remove — and removes that item out of web storage. Type the following lines into your JavaScript console:</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>localStorage.removeItem(\"name\");\nlet myName = localStorage.getItem(\"name\");\nmyName;\n</code></pre></div>\n <p>The third line should now return <code>null</code> — the <code>name</code> item no longer exists in the web storage.</p>\n </li>\n</ol>"}},{"type":"prose","value":{"id":"the_data_persists!","title":"The data persists!","isH3":true,"content":"<p>One key feature of web storage is that the data persists between page loads (and even when the browser is shut down, in the case of <code>localStorage</code>). Let's look at this in action.</p>\n<ol>\n <li>\n <p>Open our web storage blank template again, but this time in a different browser to the one you've got this tutorial open in! This will make it easier to deal with.</p>\n </li>\n <li>\n <p>Type these lines into the browser's JavaScript console:</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>localStorage.setItem(\"name\", \"Chris\");\nlet myName = localStorage.getItem(\"name\");\nmyName;\n</code></pre></div>\n <p>You should see the name item returned.</p>\n </li>\n <li>\n <p>Now close down the browser and open it up again.</p>\n </li>\n <li>\n <p>Enter the following lines again:</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>let myName = localStorage.getItem(\"name\");\nmyName;\n</code></pre></div>\n <p>You should see that the value is still available, even though the browser has been closed and then opened again.</p>\n </li>\n</ol>"}},{"type":"prose","value":{"id":"separate_storage_for_each_domain","title":"Separate storage for each domain","isH3":true,"content":"<p>There is a separate data store for each domain (each separate web address loaded in the browser). You will see that if you load two websites (say google.com and amazon.com) and try storing an item on one website, it won't be available to the other website.</p>\n<p>This makes sense — you can imagine the security issues that would arise if websites could see each other's data!</p>"}},{"type":"prose","value":{"id":"a_more_involved_example","title":"A more involved example","isH3":true,"content":"<p>Let's apply this new-found knowledge by writing a simple working example to give you an idea of how web storage can be used. Our example will allow you enter a name, after which the page will update to give you a personalized greeting. This state will also persist across page/browser reloads, because the name is stored in web storage.</p>\n<p>You can find the example HTML at <a href=\"https://github.com/mdn/learning-area/blob/master/javascript/apis/client-side-storage/web-storage/personal-greeting.html\" class=\"external\" target=\"_blank\">personal-greeting.html</a> — this contains a simple website with a header, content, and footer, and a form for entering your name.</p>\n<p>\n <img src=\"/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs/Client-side_storage/web-storage-demo.png\" alt=\"\" width=\"1024\" height=\"550\" loading=\"lazy\">\n</p>\n<p>Let's build up the example, so you can understand how it works.</p>\n<ol>\n <li>\n <p>First, make a local copy of our <a href=\"https://github.com/mdn/learning-area/blob/master/javascript/apis/client-side-storage/web-storage/personal-greeting.html\" class=\"external\" target=\"_blank\">personal-greeting.html</a> file in a new directory on your computer.</p>\n </li>\n <li>\n <p>Next, note how our HTML references a JavaScript file called <code>index.js</code> (see line 40). We need to create this and write our JavaScript code into it. Create an <code>index.js</code> file in the same directory as your HTML file.</p>\n </li>\n <li>\n <p>We'll start off by creating references to all the HTML features we need to manipulate in this example — we'll create them all as constants, as these references do not need to change in the lifecycle of the app. Add the following lines to your JavaScript file:</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>// create needed constants\nconst rememberDiv = document.querySelector(\".remember\");\nconst forgetDiv = document.querySelector(\".forget\");\nconst form = document.querySelector(\"form\");\nconst nameInput = document.querySelector(\"#entername\");\nconst submitBtn = document.querySelector(\"#submitname\");\nconst forgetBtn = document.querySelector(\"#forgetname\");\n\nconst h1 = document.querySelector(\"h1\");\nconst personalGreeting = document.querySelector(\".personal-greeting\");\n</code></pre></div>\n </li>\n <li>\n <p>Next up, we need to include a small event listener to stop the form from actually submitting itself when the submit button is pressed, as this is not the behavior we want. Add this snippet below your previous code:</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>// Stop the form from submitting when a button is pressed\nform.addEventListener(\"submit\", function (e) {\n e.preventDefault();\n});\n</code></pre></div>\n </li>\n <li>\n <p>Now we need to add an event listener, the handler function of which will run when the \"Say hello\" button is clicked. The comments explain in detail what each bit does, but in essence here we are taking the name the user has entered into the text input box and saving it in web storage using <code>setItem()</code>, then running a function called <code>nameDisplayCheck()</code> that will handle updating the actual website text. Add this to the bottom of your code:</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>// run function when the 'Say hello' button is clicked\nsubmitBtn.addEventListener(\"click\", function () {\n // store the entered name in web storage\n localStorage.setItem(\"name\", nameInput.value);\n // run nameDisplayCheck() to sort out displaying the\n // personalized greetings and updating the form display\n nameDisplayCheck();\n});\n</code></pre></div>\n </li>\n <li>\n <p>At this point we also need an event handler to run a function when the \"Forget\" button is clicked — this is only displayed after the \"Say hello\" button has been clicked (the two form states toggle back and forth). In this function we remove the <code>name</code> item from web storage using <code>removeItem()</code>, then again run <code>nameDisplayCheck()</code> to update the display. Add this to the bottom:</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>// run function when the 'Forget' button is clicked\nforgetBtn.addEventListener(\"click\", function () {\n // Remove the stored name from web storage\n localStorage.removeItem(\"name\");\n // run nameDisplayCheck() to sort out displaying the\n // generic greeting again and updating the form display\n nameDisplayCheck();\n});\n</code></pre></div>\n </li>\n <li>\n <p>It is now time to define the <code>nameDisplayCheck()</code> function itself. Here we check whether the name item has been stored in web storage by using <code>localStorage.getItem('name')</code> as a conditional test. If it has been stored, this call will evaluate to <code>true</code>; if not, it will be <code>false</code>. If it is <code>true</code>, we display a personalized greeting, display the \"forget\" part of the form, and hide the \"Say hello\" part of the form. If it is <code>false</code>, we display a generic greeting and do the opposite. Again, put the following code at the bottom:</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>// define the nameDisplayCheck() function\nfunction nameDisplayCheck() {\n // check whether the 'name' data item is stored in web Storage\n if (localStorage.getItem(\"name\")) {\n // If it is, display personalized greeting\n let name = localStorage.getItem(\"name\");\n h1.textContent = \"Welcome, \" + name;\n personalGreeting.textContent =\n \"Welcome to our website, \" +\n name +\n \"! We hope you have fun while you are here.\";\n // hide the 'remember' part of the form and show the 'forget' part\n forgetDiv.style.display = \"block\";\n rememberDiv.style.display = \"none\";\n } else {\n // if not, display generic greeting\n h1.textContent = \"Welcome to our website \";\n personalGreeting.textContent =\n \"Welcome to our website. We hope you have fun while you are here.\";\n // hide the 'forget' part of the form and show the 'remember' part\n forgetDiv.style.display = \"none\";\n rememberDiv.style.display = \"block\";\n }\n}\n</code></pre></div>\n </li>\n <li>\n <p>Last but not least, we need to run the <code>nameDisplayCheck()</code> function every time the page is loaded. If we don't do this, then the personalized greeting will not persist across page reloads. Add the following to the bottom of your code:</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>document.body.onload = nameDisplayCheck;\n</code></pre></div>\n </li>\n</ol>\n<p>Your example is finished — well done! All that remains now is to save your code and test your HTML page in a browser. You can see our <a href=\"https://mdn.github.io/learning-area/javascript/apis/client-side-storage/web-storage/personal-greeting.html\" class=\"external\" target=\"_blank\">finished version running live here</a>.</p>\n<div class=\"notecard note\">\n <p><strong>Nota:</strong> There is another, slightly more complex example to explore at <a href=\"/pt-BR/docs/Web/API/Web_Storage_API/Using_the_Web_Storage_API\">Using the Web Storage API</a>.</p>\n</div>\n<div class=\"notecard note\">\n <p><strong>Nota:</strong> In the line <code><script src=\"index.js\" defer></script></code> of the source for our finished version, the <code>defer</code> attribute specifies that the contents of the <a href=\"/pt-BR/docs/Web/HTML/Element/script\"><code><script></code></a> element will not execute until the page has finished loading.</p>\n</div>"}},{"type":"prose","value":{"id":"storing_complex_data_—_indexeddb","title":"Storing complex data — IndexedDB","isH3":false,"content":"<p>The <a href=\"/pt-BR/docs/Web/API/IndexedDB_API\">IndexedDB API</a> (sometimes abbreviated IDB) is a complete database system available in the browser in which you can store complex related data, the types of which aren't limited to simple values like strings or numbers. You can store videos, images, and pretty much anything else in an IndexedDB instance.</p>\n<p>However, this does come at a cost: IndexedDB is much more complex to use than the Web Storage API. In this section, we'll really only scratch the surface of what it is capable of, but we will give you enough to get started.</p>"}},{"type":"prose","value":{"id":"working_through_a_note_storage_example","title":"Working through a note storage example","isH3":true,"content":"<p>Here we'll run you through an example that allows you to store notes in your browser and view and delete them whenever you like, getting you to build it up for yourself and explaining the most fundamental parts of IDB as we go along.</p>\n<p>The app looks something like this:</p>\n<p>\n <img src=\"/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs/Client-side_storage/idb-demo.png\" alt=\"\" width=\"803\" height=\"736\" loading=\"lazy\">\n</p>\n<p>Each note has a title and some body text, each individually editable. The JavaScript code we'll go through below has detailed comments to help you understand what's going on.</p>"}},{"type":"prose","value":{"id":"getting_started","title":"Getting started","isH3":true,"content":"<ol>\n <li>First of all, make local copies of our <a href=\"https://github.com/mdn/learning-area/blob/master/javascript/apis/client-side-storage/indexeddb/notes/index.html\" class=\"external\" target=\"_blank\"><code>index.html</code></a>, <a href=\"https://github.com/mdn/learning-area/blob/master/javascript/apis/client-side-storage/indexeddb/notes/style.css\" class=\"external\" target=\"_blank\"><code>style.css</code></a>, and <a href=\"https://github.com/mdn/learning-area/blob/master/javascript/apis/client-side-storage/indexeddb/notes/index-start.js\" class=\"external\" target=\"_blank\"><code>index-start.js</code></a> files into a new directory on your local machine.</li>\n <li>Have a look at the files. You'll see that the HTML is pretty simple: a web site with a header and footer, as well as a main content area that contains a place to display notes, and a form for entering new notes into the database. The CSS provides some simple styling to make it clearer what is going on. The JavaScript file contains five declared constants containing references to the <a href=\"/pt-BR/docs/Web/HTML/Element/ul\"><code><ul></code></a> element the notes will be displayed in, the title and body <a href=\"/pt-BR/docs/Web/HTML/Element/input\"><code><input></code></a> elements, the <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/HTML/Element/form\"><code><form></code></a> itself, and the <a href=\"/pt-BR/docs/Web/HTML/Element/button\"><code><button></code></a>.</li>\n <li>Rename your JavaScript file to <code>index.js</code>. You are now ready to start adding code to it.</li>\n</ol>"}},{"type":"prose","value":{"id":"database_initial_set_up","title":"Database initial set up","isH3":true,"content":"<p>Now let's look at what we have to do in the first place, to actually set up a database.</p>\n<ol>\n <li>\n <p>Below the constant declarations, add the following lines:</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>// Create an instance of a db object for us to store the open database in\nlet db;\n</code></pre></div>\n <p>Here we are declaring a variable called <code>db</code> — this will later be used to store an object representing our database. We will use this in a few places, so we've declared it globally here to make things easier.</p>\n </li>\n <li>\n <p>Next, add the following to the bottom of your code:</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>window.onload = function () {};\n</code></pre></div>\n <p>We will write all of our subsequent code inside this <code>window.onload</code> event handler function, called when the window's <a href=\"/pt-BR/docs/Web/API/Window/load_event\"><code>load</code></a> event fires, to make sure we don't try to use IndexedDB functionality before the app has completely finished loading (it could fail if we don't).</p>\n </li>\n <li>\n <p>Inside the <code>window.onload</code> handler, add the following:</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>// Open our database; it is created if it doesn't already exist\n// (see onupgradeneeded below)\nlet request = window.indexedDB.open(\"notes_db\", 1);\n</code></pre></div>\n <p>This line creates a <code>request</code> to open version <code>1</code> of a database called <code>notes_db</code>. If this doesn't already exist, it will be created for you by subsequent code. You will see this request pattern used very often throughout IndexedDB. Database operations take time. You don't want to hang the browser while you wait for the results, so database operations are <a href=\"/pt-BR/docs/Glossary/Asynchronous\">asynchronous</a>, meaning that instead of happening immediately, they will happen at some point in the future, and you get notified when they're done.</p>\n <p>To handle this in IndexedDB, you create a request object (which can be called anything you like — we called it <code>request</code> so it is obvious what it is for). You then use event handlers to run code when the request completes, fails, etc., which you'll see in use below.</p>\n <div class=\"notecard note\">\n <p><strong>Nota:</strong> The version number is important. If you want to upgrade your database (for example, by changing the table structure), you have to run your code again with an increased version number, different schema specified inside the <code>onupgradeneeded</code> handler (see below), etc. We won't cover upgrading databases in this simple tutorial.</p>\n </div>\n </li>\n <li>\n <p>Now add the following event handlers just below your previous addition — again inside the <code>window.onload</code> handler:</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>// onerror handler signifies that the database didn't open successfully\nrequest.onerror = function () {\n console.log(\"Database failed to open\");\n};\n\n// onsuccess handler signifies that the database opened successfully\nrequest.onsuccess = function () {\n console.log(\"Database opened successfully\");\n\n // Store the opened database object in the db variable. This is used a lot below\n db = request.result;\n\n // Run the displayData() function to display the notes already in the IDB\n displayData();\n};\n</code></pre></div>\n <p>The <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/IDBRequest/error_event\"><code>request.onerror</code></a> handler will run if the system comes back saying that the request failed. This allows you to respond to this problem. In our simple example, we just print a message to the JavaScript console.</p>\n <p>The <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/IDBRequest/success_event\"><code>request.onsuccess</code></a> handler on the other hand will run if the request returns successfully, meaning the database was successfully opened. If this is the case, an object representing the opened database becomes available in the <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/IDBRequest/result\"><code>request.result</code></a> property, allowing us to manipulate the database. We store this in the <code>db</code> variable we created earlier for later use. We also run a custom function called <code>displayData()</code>, which displays the data in the database inside the <a href=\"/pt-BR/docs/Web/HTML/Element/ul\"><code><ul></code></a>. We run it now so that the notes already in the database are displayed as soon as the page loads. You'll see this defined later on.</p>\n </li>\n <li>\n <p>Finally for this section, we'll add probably the most important event handler for setting up the database: <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/IDBOpenDBRequest/upgradeneeded_event\"><code>request.onupgradeneeded</code></a>. This handler runs if the database has not already been set up, or if the database is opened with a bigger version number than the existing stored database (when performing an upgrade). Add the following code, below your previous handler:</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>// Setup the database tables if this has not already been done\nrequest.onupgradeneeded = function (e) {\n // Grab a reference to the opened database\n let db = e.target.result;\n\n // Create an objectStore to store our notes in (basically like a single table)\n // including a auto-incrementing key\n let objectStore = db.createObjectStore(\"notes_os\", {\n keyPath: \"id\",\n autoIncrement: true,\n });\n\n // Define what data items the objectStore will contain\n objectStore.createIndex(\"title\", \"title\", { unique: false });\n objectStore.createIndex(\"body\", \"body\", { unique: false });\n\n console.log(\"Database setup complete\");\n};\n</code></pre></div>\n <p>This is where we define the schema (structure) of our database; that is, the set of columns (or fields) it contains. Here we first grab a reference to the existing database from the <code>result</code> property of the event's target (<code>e.target.result</code>), which is the <code>request</code> object. This is equivalent to the line <code>db = request.result;</code> inside the <code>onsuccess</code> handler, but we need to do this separately here because the <code>onupgradeneeded</code> handler (if needed) will run before the <code>onsuccess</code> handler, meaning that the <code>db</code> value wouldn't be available if we didn't do this.</p>\n <p>We then use <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/IDBDatabase/createObjectStore\"><code>IDBDatabase.createObjectStore()</code></a> to create a new object store inside our opened database called <code>notes_os</code>. This is equivalent to a single table in a conventional database system. We've given it the name notes, and also specified an <code>autoIncrement</code> key field called <code>id</code> — in each new record this will automatically be given an incremented value — the developer doesn't need to set this explicitly. Being the key, the <code>id</code> field will be used to uniquely identify records, such as when deleting or displaying a record.</p>\n <p>We also create two other indexes (fields) using the <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/IDBObjectStore/createIndex\"><code>IDBObjectStore.createIndex()</code></a> method: <code>title</code> (which will contain a title for each note), and <code>body</code> (which will contain the body text of the note).</p>\n </li>\n</ol>\n<p>So with this simple database schema set up, when we start adding records to the database; each one will be represented as an object along these lines:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>{\n title: \"Buy milk\",\n body: \"Need both cows milk and soy.\",\n id: 8\n}\n</code></pre></div>"}},{"type":"prose","value":{"id":"adding_data_to_the_database","title":"Adding data to the database","isH3":true,"content":"<p>Now let's look at how we can add records to the database. This will be done using the form on our page.</p>\n<p>Below your previous event handler (but still inside the <code>window.onload</code> handler), add the following line, which sets up an <code>onsubmit</code> handler that runs a function called <code>addData()</code> when the form is submitted (when the submit <a href=\"/pt-BR/docs/Web/HTML/Element/button\"><code><button></code></a> is pressed leading to a successful form submission):</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>// Create an onsubmit handler so that when the form is submitted the addData() function is run\nform.onsubmit = addData;\n</code></pre></div>\n<p>Now let's define the <code>addData()</code> function. Add this below your previous line:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>// Define the addData() function\nfunction addData(e) {\n // prevent default - we don't want the form to submit in the conventional way\n e.preventDefault();\n\n // grab the values entered into the form fields and store them in an object ready for being inserted into the DB\n let newItem = { title: titleInput.value, body: bodyInput.value };\n\n // open a read/write db transaction, ready for adding the data\n let transaction = db.transaction([\"notes_os\"], \"readwrite\");\n\n // call an object store that's already been added to the database\n let objectStore = transaction.objectStore(\"notes_os\");\n\n // Make a request to add our newItem object to the object store\n let request = objectStore.add(newItem);\n request.onsuccess = function () {\n // Clear the form, ready for adding the next entry\n titleInput.value = \"\";\n bodyInput.value = \"\";\n };\n\n // Report on the success of the transaction completing, when everything is done\n transaction.oncomplete = function () {\n console.log(\"Transaction completed: database modification finished.\");\n\n // update the display of data to show the newly added item, by running displayData() again.\n displayData();\n };\n\n transaction.onerror = function () {\n console.log(\"Transaction not opened due to error\");\n };\n}\n</code></pre></div>\n<p>This is quite complex; breaking it down, we:</p>\n<ul>\n <li>Run <a href=\"/pt-BR/docs/Web/API/Event/preventDefault\"><code>Event.preventDefault()</code></a> on the event object to stop the form actually submitting in the conventional manner (this would cause a page refresh and spoil the experience).</li>\n <li>Create an object representing a record to enter into the database, populating it with values from the form inputs. note that we don't have to explicitly include an <code>id</code> value — as we explained earlier, this is auto-populated.</li>\n <li>Open a <code>readwrite</code> transaction against the <code>notes_os</code> object store using the <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/IDBDatabase/transaction\"><code>IDBDatabase.transaction()</code></a> method. This transaction object allows us to access the object store so we can do something to it, e.g. add a new record.</li>\n <li>Access the object store using the <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/IDBTransaction/objectStore\"><code>IDBTransaction.objectStore()</code></a> method, saving the result in the <code>objectStore</code> variable.</li>\n <li>Add the new record to the database using <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/IDBObjectStore/add\"><code>IDBObjectStore.add()</code></a>. This creates a request object, in the same fashion as we've seen before.</li>\n <li>Add a bunch of event handlers to the <code>request</code> and the <code>transaction</code> to run code at critical points in the lifecycle. Once the request has succeeded, we clear the form inputs ready for entering the next note. Once the transaction has completed, we run the <code>displayData()</code> function again to update the display of notes on the page.</li>\n</ul>"}},{"type":"prose","value":{"id":"displaying_the_data","title":"Displaying the data","isH3":true,"content":"<p>We've referenced <code>displayData()</code> twice in our code already, so we'd probably better define it. Add this to your code, below the previous function definition:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>// Define the displayData() function\nfunction displayData() {\n // Here we empty the contents of the list element each time the display is updated\n // If you didn't do this, you'd get duplicates listed each time a new note is added\n while (list.firstChild) {\n list.removeChild(list.firstChild);\n }\n\n // Open our object store and then get a cursor - which iterates through all the\n // different data items in the store\n let objectStore = db.transaction(\"notes_os\").objectStore(\"notes_os\");\n objectStore.openCursor().onsuccess = function (e) {\n // Get a reference to the cursor\n let cursor = e.target.result;\n\n // If there is still another data item to iterate through, keep running this code\n if (cursor) {\n // Create a list item, h3, and p to put each data item inside when displaying it\n // structure the HTML fragment, and append it inside the list\n const listItem = document.createElement(\"li\");\n const h3 = document.createElement(\"h3\");\n const para = document.createElement(\"p\");\n\n listItem.appendChild(h3);\n listItem.appendChild(para);\n list.appendChild(listItem);\n\n // Put the data from the cursor inside the h3 and para\n h3.textContent = cursor.value.title;\n para.textContent = cursor.value.body;\n\n // Store the ID of the data item inside an attribute on the listItem, so we know\n // which item it corresponds to. This will be useful later when we want to delete items\n listItem.setAttribute(\"data-note-id\", cursor.value.id);\n\n // Create a button and place it inside each listItem\n const deleteBtn = document.createElement(\"button\");\n listItem.appendChild(deleteBtn);\n deleteBtn.textContent = \"Delete\";\n\n // Set an event handler so that when the button is clicked, the deleteItem()\n // function is run\n deleteBtn.onclick = deleteItem;\n\n // Iterate to the next item in the cursor\n cursor.continue();\n } else {\n // Again, if list item is empty, display a 'No notes stored' message\n if (!list.firstChild) {\n const listItem = document.createElement(\"li\");\n listItem.textContent = \"No notes stored.\";\n list.appendChild(listItem);\n }\n // if there are no more cursor items to iterate through, say so\n console.log(\"Notes all displayed\");\n }\n };\n}\n</code></pre></div>\n<p>Again, let's break this down:</p>\n<ul>\n <li>First we empty out the <a href=\"/pt-BR/docs/Web/HTML/Element/ul\"><code><ul></code></a> element's content, before then filling it with the updated content. If you didn't do this, you'd end up with a huge list of duplicated content being added to with each update.</li>\n <li>Next, we get a reference to the <code>notes_os</code> object store using <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/IDBDatabase/transaction\"><code>IDBDatabase.transaction()</code></a> and <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/IDBTransaction/objectStore\"><code>IDBTransaction.objectStore()</code></a> like we did in <code>addData()</code>, except here we are chaining them together in one line.</li>\n <li>The next step is to use <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/IDBObjectStore/openCursor\"><code>IDBObjectStore.openCursor()</code></a> method to open a request for a cursor — this is a construct that can be used to iterate over the records in an object store. We chain an <code>onsuccess</code> handler on to the end of this line to make the code more concise — when the cursor is successfully returned, the handler is run.</li>\n <li>We get a reference to the cursor itself (an <a href=\"/pt-BR/docs/Web/API/IDBCursor\"><code>IDBCursor</code></a> object) using let <code>cursor = e.target.result</code>.</li>\n <li>Next, we check to see if the cursor contains a record from the datastore (<code>if(cursor){ ... }</code>) — if so, we create a DOM fragment, populate it with the data from the record, and insert it into the page (inside the <code><ul></code> element). We also include a delete button that, when clicked, will delete that note by running the <code>deleteItem()</code> function, which we will look at in the next section.</li>\n <li>At the end of the <code>if</code> block, we use the <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/IDBCursor/continue\"><code>IDBCursor.continue()</code></a> method to advance the cursor to the next record in the datastore, and run the content of the <code>if</code> block again. If there is another record to iterate to, this causes it to be inserted into the page, and then <code>continue()</code> is run again, and so on.</li>\n <li>When there are no more records to iterate over, <code>cursor</code> will return <code>undefined</code>, and therefore the <code>else</code> block will run instead of the <code>if</code> block. This block checks whether any notes were inserted into the <code><ul></code> — if not, it inserts a message to say no note was stored.</li>\n</ul>"}},{"type":"prose","value":{"id":"deleting_a_note","title":"Deleting a note","isH3":true,"content":"<p>As stated above, when a note's delete button is pressed, the note is deleted. This is achieved by the <code>deleteItem()</code> function, which looks like so:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>// Define the deleteItem() function\nfunction deleteItem(e) {\n // retrieve the name of the task we want to delete. We need\n // to convert it to a number before trying it use it with IDB; IDB key\n // values are type-sensitive.\n let noteId = Number(e.target.parentNode.getAttribute(\"data-note-id\"));\n\n // open a database transaction and delete the task, finding it using the id we retrieved above\n let transaction = db.transaction([\"notes_os\"], \"readwrite\");\n let objectStore = transaction.objectStore(\"notes_os\");\n let request = objectStore.delete(noteId);\n\n // report that the data item has been deleted\n transaction.oncomplete = function () {\n // delete the parent of the button\n // which is the list item, so it is no longer displayed\n e.target.parentNode.parentNode.removeChild(e.target.parentNode);\n console.log(\"Note \" + noteId + \" deleted.\");\n\n // Again, if list item is empty, display a 'No notes stored' message\n if (!list.firstChild) {\n let listItem = document.createElement(\"li\");\n listItem.textContent = \"No notes stored.\";\n list.appendChild(listItem);\n }\n };\n}\n</code></pre></div>\n<ul>\n <li>The first part of this could use some explaining — we retrieve the ID of the record to be deleted using <code>Number(e.target.parentNode.getAttribute('data-note-id'))</code> — recall that the ID of the record was saved in a <code>data-note-id</code> attribute on the <code><li></code> when it was first displayed. We do however need to pass the attribute through the global built-in <a href=\"/pt-BR/docs/Web/JavaScript/Reference/Global_Objects/Number\"><code>Number()</code></a> object as it is of datatype string, and therefore wouldn't be recognized by the database, which expects a number.</li>\n <li>We then get a reference to the object store using the same pattern we've seen previously, and use the <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/IDBObjectStore/delete\"><code>IDBObjectStore.delete()</code></a> method to delete the record from the database, passing it the ID.</li>\n <li>When the database transaction is complete, we delete the note's <code><li></code> from the DOM, and again do the check to see if the <code><ul></code> is now empty, inserting a note as appropriate.</li>\n</ul>\n<p>So that's it! Your example should now work.</p>\n<p>If you are having trouble with it, feel free to <a href=\"https://mdn.github.io/learning-area/javascript/apis/client-side-storage/indexeddb/notes/\" class=\"external\" target=\"_blank\">check it against our live example</a> (see the <a href=\"https://github.com/mdn/learning-area/blob/master/javascript/apis/client-side-storage/indexeddb/notes/index.js\" class=\"external\" target=\"_blank\">source code</a> also).</p>"}},{"type":"prose","value":{"id":"storing_complex_data_via_indexeddb","title":"Storing complex data via IndexedDB","isH3":true,"content":"<p>As we mentioned above, IndexedDB can be used to store more than just simple text strings. You can store just about anything you want, including complex objects such as video or image blobs. And it isn't much more difficult to achieve than any other type of data.</p>\n<p>To demonstrate how to do it, we've written another example called <a href=\"https://github.com/mdn/learning-area/tree/master/javascript/apis/client-side-storage/indexeddb/video-store\" class=\"external\" target=\"_blank\">IndexedDB video store</a> (see it <a href=\"https://mdn.github.io/learning-area/javascript/apis/client-side-storage/indexeddb/video-store/\" class=\"external\" target=\"_blank\">running live here also</a>). When you first run the example, it downloads all the videos from the network, stores them in an IndexedDB database, and then displays the videos in the UI inside <a href=\"/pt-BR/docs/Web/HTML/Element/video\"><code><video></code></a> elements. The second time you run it, it finds the videos in the database and gets them from there instead before displaying them — this makes subsequent loads much quicker and less bandwidth-hungry.</p>\n<p>Let's walk through the most interesting parts of the example. We won't look at it all — a lot of it is similar to the previous example, and the code is well-commented.</p>\n<ol>\n <li>\n <p>For this simple example, we've stored the names of the videos to fetch in an array of objects:</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>const videos = [\n { name: \"crystal\" },\n { name: \"elf\" },\n { name: \"frog\" },\n { name: \"monster\" },\n { name: \"pig\" },\n { name: \"rabbit\" },\n];\n</code></pre></div>\n </li>\n <li>\n <p>To start with, once the database is successfully opened we run an <code>init()</code> function. This loops through the different video names, trying to load a record identified by each name from the <code>videos</code> database.</p>\n <p>If each video is found in the database (easily checked by seeing whether <code>request.result</code> evaluates to <code>true</code> — if the record is not present, it will be <code>undefined</code>), its video files (stored as blobs) and the video name are passed straight to the <code>displayVideo()</code> function to place them in the UI. If not, the video name is passed to the <code>fetchVideoFromNetwork()</code> function to ... you guessed it — fetch the video from the network.</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>function init() {\n // Loop through the video names one by one\n for (let i = 0; i < videos.length; i++) {\n // Open transaction, get object store, and get() each video by name\n let objectStore = db.transaction(\"videos_os\").objectStore(\"videos_os\");\n let request = objectStore.get(videos[i].name);\n request.onsuccess = function () {\n // If the result exists in the database (is not undefined)\n if (request.result) {\n // Grab the videos from IDB and display them using displayVideo()\n console.log(\"taking videos from IDB\");\n displayVideo(\n request.result.mp4,\n request.result.webm,\n request.result.name,\n );\n } else {\n // Fetch the videos from the network\n fetchVideoFromNetwork(videos[i]);\n }\n };\n }\n}\n</code></pre></div>\n </li>\n <li>\n <p>The following snippet is taken from inside <code>fetchVideoFromNetwork()</code> — here we fetch MP4 and WebM versions of the video using two separate <a href=\"/pt-BR/docs/Web/API/Window/fetch\" title=\"WindowOrWorkerGlobalScope.fetch()\"><code>WindowOrWorkerGlobalScope.fetch()</code></a> requests. We then use the <a href=\"/pt-BR/docs/Web/API/Blob\" title=\"Body.blob()\"><code>Body.blob()</code></a> method to extract each response's body as a blob, giving us an object representation of the videos that can be stored and displayed later on.</p>\n <p>We have a problem here though — these two requests are both asynchronous, but we only want to try to display or store the video when both promises have fulfilled. Fortunately there is a built-in method that handles such a problem — <a href=\"/pt-BR/docs/Web/JavaScript/Reference/Global_Objects/Promise/all\"><code>Promise.all()</code></a>. This takes one argument — references to all the individual promises you want to check for fulfillment placed in an array — and is itself promise-based.</p>\n <p>When all those promises have fulfilled, the <code>all()</code> promise fulfills with an array containing all the individual fulfillment values. Inside the <code>all()</code> block, you can see that we then call the <code>displayVideo()</code> function like we did before to display the videos in the UI, then we also call the <code>storeVideo()</code> function to store those videos inside the database.</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>let mp4Blob = fetch(\"videos/\" + video.name + \".mp4\").then((response) =>\n response.blob(),\n);\nlet webmBlob = fetch(\"videos/\" + video.name + \".webm\").then((response) =>\n response.blob(),\n);\n\n// Only run the next code when both promises have fulfilled\nPromise.all([mp4Blob, webmBlob]).then(function (values) {\n // display the video fetched from the network with displayVideo()\n displayVideo(values[0], values[1], video.name);\n // store it in the IDB using storeVideo()\n storeVideo(values[0], values[1], video.name);\n});\n</code></pre></div>\n </li>\n <li>\n <p>Let's look at <code>storeVideo()</code> first. This is very similar to the pattern you saw in the previous example for adding data to the database — we open a <code>readwrite</code> transaction and get a reference to our <code>videos_os</code> object store, create an object representing the record to add to the database, then simply add it using <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/IDBObjectStore/add\"><code>IDBObjectStore.add()</code></a>.</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>function storeVideo(mp4Blob, webmBlob, name) {\n // Open transaction, get object store; make it a readwrite so we can write to the IDB\n let objectStore = db.transaction(['videos_os'], 'readwrite').objectStore('videos_os');\n // Create a record to add to the IDB\n let record = {\n mp4 : mp4Blob,\n webm : webmBlob,\n name : name\n }\n\n // Add the record to the IDB using add()\n let request = objectStore.add(record);\n\n ...\n\n};\n</code></pre></div>\n </li>\n <li>\n <p>Last but not least, we have <code>displayVideo()</code>, which creates the DOM elements needed to insert the video in the UI and then appends them to the page. The most interesting parts of this are those shown below — to actually display our video blobs in a <code><video></code> element, we need to create object URLs (internal URLs that point to the video blobs stored in memory) using the <a href=\"/pt-BR/docs/Web/API/URL/createObjectURL_static\"><code>URL.createObjectURL()</code></a> method. Once that is done, we can set the object URLs to be the values of our <a href=\"/pt-BR/docs/Web/HTML/Element/source\"><code><source></code></a> element's <code>src</code> attributes, and it works fine.</p>\n <div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>function displayVideo(mp4Blob, webmBlob, title) {\n // Create object URLs out of the blobs\n let mp4URL = URL.createObjectURL(mp4Blob);\n let webmURL = URL.createObjectURL(webmBlob);\n\n ...\n\n const video = document.createElement('video');\n video.controls = true;\n const source1 = document.createElement('source');\n source1.src = mp4URL;\n source1.type = 'video/mp4';\n const source2 = document.createElement('source');\n source2.src = webmURL;\n source2.type = 'video/webm';\n\n ...\n}\n</code></pre></div>\n </li>\n</ol>"}},{"type":"prose","value":{"id":"offline_asset_storage","title":"Offline asset storage","isH3":false,"content":"<p>The above example already shows how to create an app that will store large assets in an IndexedDB database, avoiding the need to download them more than once. This is already a great improvement to the user experience, but there is still one thing missing — the main HTML, CSS, and JavaScript files still need to be downloaded each time the site is accessed, meaning that it won't work when there is no network connection.</p>\n<p>\n <img src=\"/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs/Client-side_storage/ff-offline.png\" alt=\"\" width=\"765\" height=\"307\" loading=\"lazy\">\n</p>\n<p>This is where <a href=\"/pt-BR/docs/Web/API/Service_Worker_API\">Service workers</a> and the closely-related <a href=\"/pt-BR/docs/Web/API/Cache\">Cache API</a> come in.</p>\n<p>A service worker is a JavaScript file that, simply put, is registered against a particular origin (web site, or part of a web site at a certain domain) when it is accessed by a browser. When registered, it can control pages available at that origin. It does this by sitting between a loaded page and the network and intercepting network requests aimed at that origin.</p>\n<p>When it intercepts a request, it can do anything you wish to it (see <a href=\"/pt-BR/docs/Web/API/Service_Worker_API#other_use_case_ideas\">use case ideas</a>), but the classic example is saving the network responses offline and then providing those in response to a request instead of the responses from the network. In effect, it allows you to make a web site work completely offline.</p>\n<p>The Cache API is a another client-side storage mechanism, with a bit of a difference — it is designed to save HTTP responses, and so works very well with service workers.</p>\n<div class=\"notecard note\">\n <p><strong>Nota:</strong> Service workers and Cache are supported in most modern browsers now. At the time of writing, Safari was still busy implementing it, but it should be there soon.</p>\n</div>"}},{"type":"prose","value":{"id":"a_service_worker_example","title":"A service worker example","isH3":true,"content":"<p>Let's look at an example, to give you a bit of an idea of what this might look like. We have created another version of the video store example we saw in the previous section — this functions identically, except that it also saves the HTML, CSS, and JavaScript in the Cache API via a service worker, allowing the example to run offline!</p>\n<p>See <a href=\"https://mdn.github.io/learning-area/javascript/apis/client-side-storage/cache-sw/video-store-offline/\" class=\"external\" target=\"_blank\">IndexedDB video store with service worker running live</a>, and also <a href=\"https://github.com/mdn/learning-area/tree/master/javascript/apis/client-side-storage/cache-sw/video-store-offline\" class=\"external\" target=\"_blank\">see the source code</a>.</p>\n<h4 id=\"registering_the_service_worker\">Registering the service worker</h4>\n<p>The first thing to note is that there's an extra bit of code placed in the main JavaScript file (see <a href=\"https://github.com/mdn/learning-area/blob/master/javascript/apis/client-side-storage/cache-sw/video-store-offline/index.js\" class=\"external\" target=\"_blank\">index.js</a>). First we do a feature detection test to see if the <code>serviceWorker</code> member is available in the <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/Navigator\"><code>Navigator</code></a> object. If this returns true, then we know that at least the basics of service workers are supported. Inside here we use the <a href=\"/pt-BR/docs/Web/API/ServiceWorkerContainer/register\"><code>ServiceWorkerContainer.register()</code></a> method to register a service worker contained in the <code>sw.js</code> file against the origin it resides at, so it can control pages in the same directory as it, or subdirectories. When its promise fulfills, the service worker is deemed registered.</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>// Register service worker to control making site work offline\n\nif (\"serviceWorker\" in navigator) {\n navigator.serviceWorker\n .register(\n \"/learning-area/javascript/apis/client-side-storage/cache-sw/video-store-offline/sw.js\",\n )\n .then(function () {\n console.log(\"Service Worker Registered\");\n });\n}\n</code></pre></div>\n<div class=\"notecard note\">\n <p><strong>Nota:</strong> The given path to the <code>sw.js</code> file is relative to the site origin, not the JavaScript file that contains the code. The service worker is at <code>https://mdn.github.io/learning-area/javascript/apis/client-side-storage/cache-sw/video-store-offline/sw.js</code>. The origin is <code>https://mdn.github.io</code>, and therefore the given path has to be <code>/learning-area/javascript/apis/client-side-storage/cache-sw/video-store-offline/sw.js</code>. If you wanted to host this example on your own server, you'd have to change this accordingly. This is rather confusing, but it has to work this way for security reasons.</p>\n</div>\n<h4 id=\"installing_the_service_worker\">Installing the service worker</h4>\n<p>The next time any page under the service worker's control is accessed (e.g. when the example is reloaded), the service worker is installed against that page, meaning that it will start controlling it. When this occurs, an <code>install</code> event is fired against the service worker; you can write code inside the service worker itself that will respond to the installation.</p>\n<p>Let's look at an example, in the <a href=\"https://github.com/mdn/learning-area/blob/master/javascript/apis/client-side-storage/cache-sw/video-store-offline/sw.js\" class=\"external\" target=\"_blank\">sw.js</a> file (the service worker). You'll see that the install listener is registered against <code>self</code>. This <code>self</code> keyword is a way to refer to the global scope of the service worker from inside the service worker file.</p>\n<p>Inside the <code>install</code> handler we use the <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/ExtendableEvent/waitUntil\"><code>ExtendableEvent.waitUntil()</code></a> method, available on the event object, to signal that the browser shouldn't complete installation of the service worker until after the promise inside it has fulfilled successfully.</p>\n<p>Here is where we see the Cache API in action. We use the <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/CacheStorage/open\"><code>CacheStorage.open()</code></a> method to open a new cache object in which responses can be stored (similar to an IndexedDB object store). This promise fulfills with a <a href=\"/pt-BR/docs/Web/API/Cache\"><code>Cache</code></a> object representing the <code>video-store</code> cache. We then use the <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/Cache/addAll\"><code>Cache.addAll()</code></a> method to fetch a series of assets and add their responses to the cache.</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>self.addEventListener(\"install\", function (e) {\n e.waitUntil(\n caches.open(\"video-store\").then(function (cache) {\n return cache.addAll([\n \"/learning-area/javascript/apis/client-side-storage/cache-sw/video-store-offline/\",\n \"/learning-area/javascript/apis/client-side-storage/cache-sw/video-store-offline/index.html\",\n \"/learning-area/javascript/apis/client-side-storage/cache-sw/video-store-offline/index.js\",\n \"/learning-area/javascript/apis/client-side-storage/cache-sw/video-store-offline/style.css\",\n ]);\n }),\n );\n});\n</code></pre></div>\n<p>That's it for now, installation done.</p>\n<h4 id=\"responding_to_further_requests\">Responding to further requests</h4>\n<p>With the service worker registered and installed against our HTML page, and the relevant assets all added to our cache, we are nearly ready to go. There is only one more thing to do, write some code to respond to further network requests.</p>\n<p>This is what the second bit of code in <code>sw.js</code> does. We add another listener to the service worker global scope, which runs the handler function when the <code>fetch</code> event is raised. This happens whenever the browser makes a request for an asset in the directory the service worker is registered against.</p>\n<p>Inside the handler we first log the URL of the requested asset. We then provide a custom response to the request, using the <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/FetchEvent/respondWith\"><code>FetchEvent.respondWith()</code></a> method.</p>\n<p>Inside this block we use <a class=\"only-in-en-us\" title=\"Esta página está disponível apenas em inglês no momento\" href=\"/en-US/docs/Web/API/CacheStorage/match\"><code>CacheStorage.match()</code></a> to check whether a matching request (i.e. matches the URL) can be found in any cache. This promise fulfills with the matching response if a match is found, or <code>undefined</code> if it isn't.</p>\n<p>If a match is found, we simply return it as the custom response. If not, we <a href=\"/pt-BR/docs/Web/API/Window/fetch\">fetch()</a> the response from the network and return that instead.</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>self.addEventListener(\"fetch\", function (e) {\n console.log(e.request.url);\n e.respondWith(\n caches.match(e.request).then(function (response) {\n return response || fetch(e.request);\n }),\n );\n});\n</code></pre></div>\n<p>And that is it for our simple service worker. There is a whole load more you can do with them — for a lot more detail, see the <a href=\"https://github.com/mdn/serviceworker-cookbook/\" class=\"external\" target=\"_blank\">service worker cookbook</a>. And thanks to Paul Kinlan for his article <a href=\"https://developers.google.com/web/fundamentals/codelabs/offline/\" class=\"external\" target=\"_blank\">Adding a Service Worker and Offline into your Web App</a>, which inspired this simple example.</p>\n<h4 id=\"testing_the_example_offline\">Testing the example offline</h4>\n<p>To test our <a href=\"https://mdn.github.io/learning-area/javascript/apis/client-side-storage/cache-sw/video-store-offline/\" class=\"external\" target=\"_blank\">service worker example</a>, you'll need to load it a couple of times to make sure it is installed. Once this is done, you can:</p>\n<ul>\n <li>Try unplugging your network/turning your Wifi off.</li>\n <li>Select <em>File > Work Offline</em> if you are using Firefox.</li>\n <li>Go to the devtools, then choose <em>Application > Service Workers</em>, then check the <em>Offline</em> checkbox if you are using Chrome.</li>\n</ul>\n<p>If you refresh your example page again, you should still see it load just fine. Everything is stored offline — the page assets in a cache, and the videos in an IndexedDB database.</p>"}},{"type":"prose","value":{"id":"summary","title":"Summary","isH3":false,"content":"<p>That's it for now. We hope you've found our rundown of client-side storage technologies useful.</p>"}},{"type":"prose","value":{"id":"see_also","title":"See also","isH3":false,"content":"<ul>\n <li><a href=\"/pt-BR/docs/Web/API/Web_Storage_API\">Web storage API</a></li>\n <li><a href=\"/pt-BR/docs/Web/API/IndexedDB_API\">IndexedDB API</a></li>\n <li><a href=\"/pt-BR/docs/Web/HTTP/Cookies\">Cookies</a></li>\n <li><a href=\"/pt-BR/docs/Web/API/Service_Worker_API\">Service worker API</a></li>\n</ul><ul class=\"prev-next\">\n <li><a class=\"button secondary only-in-en-us\" href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Video_and_audio_APIs\" title=\"Esta página está disponível apenas em inglês no momento\"><span class=\"button-wrap\"> Anterior </span></a></li>\n <li><a class=\"button secondary\" href=\"/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs\"><span class=\"button-wrap\"> Menu: APIs web do lado cliente</span></a></li>\n \n</ul>"}}],"toc":[{"text":"Armazenamento do lado do cliente?","id":"armazenamento_do_lado_do_cliente"},{"text":"Storing simple data — web storage","id":"storing_simple_data_—_web_storage"},{"text":"Storing complex data — IndexedDB","id":"storing_complex_data_—_indexeddb"},{"text":"Offline asset storage","id":"offline_asset_storage"},{"text":"Summary","id":"summary"},{"text":"See also","id":"see_also"}],"summary":"That's it for now. We hope you've found our rundown of client-side storage technologies useful.","popularity":0,"modified":"2024-11-21T07:55:48.000Z","other_translations":[{"locale":"de","title":"Client-side storage","native":"Deutsch"},{"locale":"en-US","title":"Client-side storage","native":"English (US)"},{"locale":"es","title":"Almacenamiento del lado cliente","native":"Español"},{"locale":"fr","title":"Stockage côté client","native":"Français"},{"locale":"ja","title":"クライアント側ストレージ","native":"日本語"},{"locale":"ru","title":"Client-side storage","native":"Русский"},{"locale":"zh-CN","title":"客户端存储","native":"中文 (简体)"}],"pageType":"unknown","source":{"folder":"pt-br/learn/javascript/client-side_web_apis/client-side_storage","github_url":"https://github.com/mdn/translated-content/blob/main/files/pt-br/learn/javascript/client-side_web_apis/client-side_storage/index.md","last_commit_url":"https://github.com/mdn/translated-content/commit/a559d2fcdfec11ace3fe55fa8ee6d6d147f7f2c3","filename":"index.md"},"short_title":"Client-side storage","parents":[{"uri":"/pt-BR/docs/Learn","title":"Aprendendo desenvolvimento web"},{"uri":"/pt-BR/docs/Learn/JavaScript","title":"JavaScript"},{"uri":"/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs","title":"APIs web do lado cliente"},{"uri":"/pt-BR/docs/Learn/JavaScript/Client-side_web_APIs/Client-side_storage","title":"Client-side storage"}],"pageTitle":"Client-side storage - Aprendendo desenvolvimento web | MDN","noIndexing":false}}</script></body></html>