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Metadata in HTML</a></li><li><a href="/en-US/docs/Learn/HTML/Introduction_to_HTML/HTML_text_fundamentals">HTML text fundamentals</a></li><li><a href="/en-US/docs/Learn/HTML/Introduction_to_HTML/Creating_hyperlinks">Creating hyperlinks</a></li><li><a href="/en-US/docs/Learn/HTML/Introduction_to_HTML/Advanced_text_formatting">Advanced text formatting</a></li><li><a href="/en-US/docs/Learn/HTML/Introduction_to_HTML/Document_and_website_structure">Document and website structure</a></li><li><a href="/en-US/docs/Learn/HTML/Introduction_to_HTML/Debugging_HTML">Debugging HTML</a></li><li><a href="/en-US/docs/Learn/HTML/Introduction_to_HTML/Marking_up_a_letter">Marking up a letter</a></li><li><a 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>Multimedia and embedding</summary><ol><li><a href="/en-US/docs/Learn/HTML/Multimedia_and_embedding">Multimedia and embedding</a></li><li><a href="/en-US/docs/Learn/HTML/Multimedia_and_embedding/Images_in_HTML">Images in HTML</a></li><li><a href="/en-US/docs/Learn/HTML/Multimedia_and_embedding/Video_and_audio_content">Video and audio content</a></li><li><a href="/en-US/docs/Learn/HTML/Multimedia_and_embedding/Other_embedding_technologies">From object to iframe — other embedding technologies</a></li><li><a href="/en-US/docs/Learn/HTML/Multimedia_and_embedding/Adding_vector_graphics_to_the_Web">Adding vector graphics to the web</a></li><li><a href="/en-US/docs/Learn/HTML/Multimedia_and_embedding/Responsive_images">Responsive images</a></li><li><a href="/en-US/docs/Learn/HTML/Multimedia_and_embedding/Mozilla_splash_page">Mozilla splash page</a></li></ol></details></li><li><details><summary>HTML tables</summary><ol><li><a href="/en-US/docs/Learn/HTML/Tables">HTML tables</a></li><li><a href="/en-US/docs/Learn/HTML/Tables/Basics">HTML table basics</a></li><li><a href="/en-US/docs/Learn/HTML/Tables/Advanced">HTML table advanced features and accessibility</a></li><li><a href="/en-US/docs/Learn/HTML/Tables/Structuring_planet_data">Structuring planet data</a></li></ol></details></li><li class="section"><a href="/en-US/docs/Learn/CSS">CSS — Styling the web</a></li><li><details><summary>CSS first steps</summary><ol><li><a href="/en-US/docs/Learn/CSS/First_steps">CSS first steps</a></li><li><a href="/en-US/docs/Learn/CSS/First_steps/What_is_CSS">What is CSS?</a></li><li><a href="/en-US/docs/Learn/CSS/First_steps/Getting_started">Getting started with CSS</a></li><li><a href="/en-US/docs/Learn/CSS/First_steps/How_CSS_is_structured">How CSS is structured</a></li><li><a href="/en-US/docs/Learn/CSS/First_steps/How_CSS_works">How CSS works</a></li><li><a href="/en-US/docs/Learn/CSS/First_steps/Styling_a_biography_page">Styling a biography page</a></li></ol></details></li><li><details><summary>CSS building blocks</summary><ol><li><a href="/en-US/docs/Learn/CSS/Building_blocks">CSS building blocks</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/Selectors">CSS selectors</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/Selectors/Type_Class_and_ID_Selectors">Type, class, and ID selectors</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/Selectors/Attribute_selectors">Attribute selectors</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/Selectors/Pseudo-classes_and_pseudo-elements">Pseudo-classes and pseudo-elements</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/Selectors/Combinators">Combinators</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/Cascade_and_inheritance">Cascade, specificity, and inheritance</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/Cascade_layers">Cascade layers</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/The_box_model">The box model</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/Backgrounds_and_borders">Backgrounds and borders</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/Handling_different_text_directions">Handling different text directions</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/Overflowing_content">Overflowing content</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/Values_and_units">CSS values and units</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/Sizing_items_in_CSS">Sizing items in CSS</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/Images_media_form_elements">Images, media, and form elements</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/Styling_tables">Styling tables</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/Advanced_styling_effects">Advanced styling effects</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/Debugging_CSS">Debugging CSS</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/Organizing">Organizing your CSS</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/Fundamental_CSS_comprehension">Fundamental CSS comprehension</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/Creating_fancy_letterheaded_paper">Creating fancy letterheaded paper</a></li><li><a href="/en-US/docs/Learn/CSS/Building_blocks/A_cool_looking_box">A cool-looking box</a></li></ol></details></li><li><details><summary>Styling text</summary><ol><li><a href="/en-US/docs/Learn/CSS/Styling_text">CSS styling text</a></li><li><a href="/en-US/docs/Learn/CSS/Styling_text/Fundamentals">Fundamental text and font styling</a></li><li><a href="/en-US/docs/Learn/CSS/Styling_text/Styling_lists">Styling lists</a></li><li><a href="/en-US/docs/Learn/CSS/Styling_text/Styling_links">Styling links</a></li><li><a href="/en-US/docs/Learn/CSS/Styling_text/Web_fonts">Web fonts</a></li><li><a href="/en-US/docs/Learn/CSS/Styling_text/Typesetting_a_homepage">Typesetting a community school homepage</a></li></ol></details></li><li><details><summary>CSS layout</summary><ol><li><a href="/en-US/docs/Learn/CSS/CSS_layout">CSS layout</a></li><li><a href="/en-US/docs/Learn/CSS/CSS_layout/Introduction">Introduction to CSS layout</a></li><li><a href="/en-US/docs/Learn/CSS/CSS_layout/Normal_Flow">Normal Flow</a></li><li><a href="/en-US/docs/Learn/CSS/CSS_layout/Flexbox">Flexbox</a></li><li><a href="/en-US/docs/Learn/CSS/CSS_layout/Grids">Grids</a></li><li><a href="/en-US/docs/Learn/CSS/CSS_layout/Floats">Floats</a></li><li><a href="/en-US/docs/Learn/CSS/CSS_layout/Positioning">Positioning</a></li><li><a href="/en-US/docs/Learn/CSS/CSS_layout/Multiple-column_Layout">Multiple-column layout</a></li><li><a href="/en-US/docs/Learn/CSS/CSS_layout/Responsive_Design">Responsive design</a></li><li><a href="/en-US/docs/Learn/CSS/CSS_layout/Media_queries">Beginner's guide to media queries</a></li><li><a href="/en-US/docs/Learn/CSS/CSS_layout/Legacy_Layout_Methods">Legacy layout methods</a></li><li><a href="/en-US/docs/Learn/CSS/CSS_layout/Supporting_Older_Browsers">Supporting older browsers</a></li><li><a href="/en-US/docs/Learn/CSS/CSS_layout/Fundamental_Layout_Comprehension">Fundamental layout comprehension</a></li></ol></details></li><li class="section"><a href="/en-US/docs/Learn/JavaScript">JavaScript — Dynamic client-side scripting</a></li><li><details><summary>JavaScript first steps</summary><ol><li><a href="/en-US/docs/Learn/JavaScript/First_steps">JavaScript first steps</a></li><li><a href="/en-US/docs/Learn/JavaScript/First_steps/What_is_JavaScript">What is JavaScript?</a></li><li><a href="/en-US/docs/Learn/JavaScript/First_steps/A_first_splash">A first splash into JavaScript</a></li><li><a href="/en-US/docs/Learn/JavaScript/First_steps/What_went_wrong">What went wrong? Troubleshooting JavaScript</a></li><li><a href="/en-US/docs/Learn/JavaScript/First_steps/Variables">Storing the information you need — Variables</a></li><li><a href="/en-US/docs/Learn/JavaScript/First_steps/Math">Basic math in JavaScript — numbers and operators</a></li><li><a href="/en-US/docs/Learn/JavaScript/First_steps/Strings">Handling text — strings in JavaScript</a></li><li><a href="/en-US/docs/Learn/JavaScript/First_steps/Useful_string_methods">Useful string methods</a></li><li><a href="/en-US/docs/Learn/JavaScript/First_steps/Arrays">Arrays</a></li><li><a href="/en-US/docs/Learn/JavaScript/First_steps/Silly_story_generator">Silly story generator</a></li></ol></details></li><li><details><summary>JavaScript building blocks</summary><ol><li><a href="/en-US/docs/Learn/JavaScript/Building_blocks">JavaScript building blocks</a></li><li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/conditionals">Making decisions in your code — conditionals</a></li><li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code">Looping code</a></li><li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Functions">Functions — reusable blocks of code</a></li><li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Build_your_own_function">Build your own function</a></li><li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Return_values">Function return values</a></li><li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Events">Introduction to events</a></li><li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Event_bubbling">Event bubbling</a></li><li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Image_gallery">Image gallery</a></li></ol></details></li><li><details><summary>Introducing JavaScript objects</summary><ol><li><a href="/en-US/docs/Learn/JavaScript/Objects">Introducing JavaScript objects</a></li><li><a href="/en-US/docs/Learn/JavaScript/Objects/Basics">JavaScript object basics</a></li><li><a href="/en-US/docs/Learn/JavaScript/Objects/Object_prototypes">Object prototypes</a></li><li><a href="/en-US/docs/Learn/JavaScript/Objects/Object-oriented_programming">Object-oriented programming</a></li><li><a href="/en-US/docs/Learn/JavaScript/Objects/Classes_in_JavaScript">Classes in JavaScript</a></li><li><a href="/en-US/docs/Learn/JavaScript/Objects/JSON">Working with JSON</a></li><li><a href="/en-US/docs/Learn/JavaScript/Objects/Object_building_practice">Object building practice</a></li><li><a href="/en-US/docs/Learn/JavaScript/Objects/Adding_bouncing_balls_features">Adding features to our bouncing balls demo</a></li></ol></details></li><li><details><summary>Asynchronous JavaScript</summary><ol><li><a href="/en-US/docs/Learn/JavaScript/Asynchronous">Asynchronous JavaScript</a></li><li><a href="/en-US/docs/Learn/JavaScript/Asynchronous/Introducing">Introducing asynchronous JavaScript</a></li><li><a href="/en-US/docs/Learn/JavaScript/Asynchronous/Promises">How to use promises</a></li><li><a href="/en-US/docs/Learn/JavaScript/Asynchronous/Implementing_a_promise-based_API">How to implement a promise-based API</a></li><li><a href="/en-US/docs/Learn/JavaScript/Asynchronous/Introducing_workers">Introducing workers</a></li><li><a href="/en-US/docs/Learn/JavaScript/Asynchronous/Sequencing_animations">Sequencing animations</a></li></ol></details></li><li><details><summary>Client-side web APIs</summary><ol><li><a href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs">Client-side web APIs</a></li><li><a href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Introduction">Introduction to web APIs</a></li><li><a href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Manipulating_documents">Manipulating documents</a></li><li><a href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Fetching_data">Fetching data from the server</a></li><li><a href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Third_party_APIs">Third-party APIs</a></li><li><a href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Drawing_graphics">Drawing graphics</a></li><li><a href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Video_and_audio_APIs">Video and Audio APIs</a></li><li><a href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Client-side_storage">Client-side storage</a></li></ol></details></li><li class="section"><a href="/en-US/docs/Learn/Forms">Web forms — Working with user data</a></li><li><details><summary>Web form building blocks</summary><ol><li><a href="/en-US/docs/Learn/Forms">Web form building blocks</a></li><li><a href="/en-US/docs/Learn/Forms/Your_first_form">Your first form</a></li><li><a href="/en-US/docs/Learn/Forms/How_to_structure_a_web_form">How to structure a web form</a></li><li><a href="/en-US/docs/Learn/Forms/Basic_native_form_controls">Basic native form controls</a></li><li><a href="/en-US/docs/Learn/Forms/HTML5_input_types">The HTML5 input types</a></li><li><a href="/en-US/docs/Learn/Forms/Other_form_controls">Other form controls</a></li><li><a href="/en-US/docs/Learn/Forms/Styling_web_forms">Styling web forms</a></li><li><a href="/en-US/docs/Learn/Forms/Advanced_form_styling">Advanced form styling</a></li><li><a href="/en-US/docs/Learn/Forms/UI_pseudo-classes">UI pseudo-classes</a></li><li><a href="/en-US/docs/Learn/Forms/Form_validation">Client-side form validation</a></li><li><a href="/en-US/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 href="/en-US/docs/Learn/Forms/How_to_build_custom_form_controls">How to build custom form controls</a></li><li><a href="/en-US/docs/Learn/Forms/Sending_forms_through_JavaScript">Sending forms through JavaScript</a></li><li><a href="/en-US/docs/Learn/Forms/Property_compatibility_table_for_form_controls">CSS property compatibility table for form controls</a></li><li><a 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="/en-US/docs/Learn/Accessibility">Accessibility — Make the web usable by everyone</a></li><li><details><summary>Accessibility guides</summary><ol><li><a href="/en-US/docs/Learn/Accessibility">Accessibility</a></li><li><a href="/en-US/docs/Learn/Accessibility/What_is_accessibility">What is accessibility?</a></li><li><a href="/en-US/docs/Learn/Accessibility/HTML">HTML: A good basis for accessibility</a></li><li><a href="/en-US/docs/Learn/Accessibility/CSS_and_JavaScript">CSS and JavaScript accessibility best practices</a></li><li><a href="/en-US/docs/Learn/Accessibility/WAI-ARIA_basics">WAI-ARIA basics</a></li><li><a href="/en-US/docs/Learn/Accessibility/Multimedia">Accessible multimedia</a></li><li><a href="/en-US/docs/Learn/Accessibility/Mobile">Mobile accessibility</a></li><li><a href="/en-US/docs/Learn/Accessibility/Accessibility_troubleshooting">Assessment: Accessibility troubleshooting</a></li></ol></details></li><li class="section"><a href="/en-US/docs/Learn/Performance">Performance — Making websites fast and responsive</a></li><li><details><summary>Performance guides</summary><ol><li><a href="/en-US/docs/Learn/Performance">Web performance</a></li><li><a href="/en-US/docs/Learn/Performance/why_web_performance">The "why" of web performance</a></li><li><a href="/en-US/docs/Learn/Performance/What_is_web_performance">What is web performance?</a></li><li><a href="/en-US/docs/Learn/Performance/Perceived_performance">Perceived performance</a></li><li><a href="/en-US/docs/Learn/Performance/Measuring_performance">Measuring performance</a></li><li><a href="/en-US/docs/Learn/Performance/Multimedia">Multimedia: Images</a></li><li><a href="/en-US/docs/Learn/Performance/video">Multimedia: video</a></li><li><a href="/en-US/docs/Learn/Performance/JavaScript">JavaScript performance optimization</a></li><li><a href="/en-US/docs/Learn/Performance/HTML">HTML performance optimization</a></li><li><a href="/en-US/docs/Learn/Performance/CSS">CSS performance optimization</a></li><li><a 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="/en-US/docs/Learn/MathML">MathML — Writing mathematics with MathML</a></li><li><details><summary>MathML first steps</summary><ol><li><a href="/en-US/docs/Learn/MathML/First_steps">MathML first steps</a></li><li><a href="/en-US/docs/Learn/MathML/First_steps/Getting_started">Getting started with MathML</a></li><li><a href="/en-US/docs/Learn/MathML/First_steps/Text_containers">MathML Text Containers</a></li><li><a href="/en-US/docs/Learn/MathML/First_steps/Fractions_and_roots">MathML fractions and roots</a></li><li><a href="/en-US/docs/Learn/MathML/First_steps/Scripts">MathML scripted elements</a></li><li><a href="/en-US/docs/Learn/MathML/First_steps/Tables">MathML tables</a></li><li><a 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="/en-US/docs/Learn/../Games">Games — Developing games for the web</a></li><li><details><summary>Guides and tutorials</summary><ol><li><a href="/en-US/docs/Games/Introduction">Introduction to game development for the Web</a></li><li><a href="/en-US/docs/Games/Techniques">Techniques for game development</a></li><li><a href="/en-US/docs/Games/Tutorials">Tutorials</a></li><li><a href="/en-US/docs/Games/Publishing_games">Publishing games</a></li></ol></details></li><li class="section"><a href="/en-US/docs/Learn/Tools_and_testing">Tools and testing</a></li><li><details><summary>Client-side web development tools</summary><ol><li><a href="/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools">Understanding client-side web development tools</a></li><li><a href="/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Overview">Client-side tooling overview</a></li><li><a href="/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Command_line">Command line crash course</a></li><li><a href="/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Package_management">Package management basics</a></li><li><a href="/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Introducing_complete_toolchain">Introducing a complete toolchain</a></li><li><a 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 href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Introduction">Introduction to client-side frameworks</a></li><li><a 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="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_getting_started">Getting started with React</a></li><li><a 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 href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_components">Componentizing our React app</a></li><li><a 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 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 href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_accessibility">Accessibility in React</a></li><li><a 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 href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_getting_started">Getting started with Ember</a></li><li><a href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_structure_componentization">Ember app structure and componentization</a></li><li><a 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 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 href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_routing">Routing in Ember</a></li><li><a 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="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_getting_started">Getting started with Vue</a></li><li><a href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_first_component">Creating our first Vue component</a></li><li><a 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 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 href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_styling">Styling Vue components with CSS</a></li><li><a href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_computed_properties">Using Vue computed properties</a></li><li><a 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 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 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 href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_getting_started">Getting started with Svelte</a></li><li><a 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 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 href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_components">Componentizing our Svelte app</a></li><li><a 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 href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_stores">Working with Svelte stores</a></li><li><a href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_TypeScript">TypeScript support in Svelte</a></li><li><a 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 href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_getting_started">Getting started with Angular</a></li><li><a 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 href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_styling">Styling our Angular app</a></li><li><a href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_item_component">Creating an item component</a></li><li><a href="/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_filtering">Filtering our to-do items</a></li><li><a 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 href="/en-US/docs/Learn/Tools_and_testing/GitHub">Git and GitHub</a></li></ol></details></li><li><details><summary>Cross browser testing</summary><ol><li><a href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing">Cross browser testing</a></li><li><a href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Introduction">Introduction to cross-browser testing</a></li><li><a href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Testing_strategies">Strategies for carrying out testing</a></li><li><a href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/HTML_and_CSS">Handling common HTML and CSS problems</a></li><li><a href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/JavaScript">Handling common JavaScript problems</a></li><li><a href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Accessibility">Handling common accessibility problems</a></li><li><a href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Feature_detection">Implementing feature detection</a></li><li><a href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Automated_testing">Introduction to automated testing</a></li><li><a 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="/en-US/docs/Learn/Server-side">Server-side website programming</a></li><li><details><summary>First steps</summary><ol><li><a href="/en-US/docs/Learn/Server-side/First_steps">Server-side website programming first steps</a></li><li><a href="/en-US/docs/Learn/Server-side/First_steps/Introduction">Introduction to the server side</a></li><li><a href="/en-US/docs/Learn/Server-side/First_steps/Client-Server_overview">Client-Server Overview</a></li><li><a href="/en-US/docs/Learn/Server-side/First_steps/Web_frameworks">Server-side web frameworks</a></li><li><a href="/en-US/docs/Learn/Server-side/First_steps/Website_security">Website security</a></li></ol></details></li><li><details><summary>Django web framework (Python)</summary><ol><li><a href="/en-US/docs/Learn/Server-side/Django">Django Web Framework (Python)</a></li><li><a href="/en-US/docs/Learn/Server-side/Django/Introduction">Django introduction</a></li><li><a href="/en-US/docs/Learn/Server-side/Django/development_environment">Setting up a Django development environment</a></li><li><a href="/en-US/docs/Learn/Server-side/Django/Tutorial_local_library_website">Django Tutorial: The Local Library website</a></li><li><a href="/en-US/docs/Learn/Server-side/Django/skeleton_website">Django Tutorial Part 2: Creating a skeleton website</a></li><li><a href="/en-US/docs/Learn/Server-side/Django/Models">Django Tutorial Part 3: Using models</a></li><li><a href="/en-US/docs/Learn/Server-side/Django/Admin_site">Django Tutorial Part 4: Django admin site</a></li><li><a href="/en-US/docs/Learn/Server-side/Django/Home_page">Django Tutorial Part 5: Creating our home page</a></li><li><a href="/en-US/docs/Learn/Server-side/Django/Generic_views">Django Tutorial Part 6: Generic list and detail views</a></li><li><a href="/en-US/docs/Learn/Server-side/Django/Sessions">Django Tutorial Part 7: Sessions framework</a></li><li><a href="/en-US/docs/Learn/Server-side/Django/Authentication">Django Tutorial Part 8: User authentication and permissions</a></li><li><a href="/en-US/docs/Learn/Server-side/Django/Forms">Django Tutorial Part 9: Working with forms</a></li><li><a href="/en-US/docs/Learn/Server-side/Django/Testing">Django Tutorial Part 10: Testing a Django web application</a></li><li><a href="/en-US/docs/Learn/Server-side/Django/Deployment">Django Tutorial Part 11: Deploying Django to production</a></li><li><a href="/en-US/docs/Learn/Server-side/Django/web_application_security">Django web application security</a></li><li><a href="/en-US/docs/Learn/Server-side/Django/django_assessment_blog">Assessment: DIY Django mini blog</a></li></ol></details></li><li><details><summary>Express Web Framework (Node.js/JavaScript)</summary><ol><li><a href="/en-US/docs/Learn/Server-side/Express_Nodejs">Express web framework (Node.js/JavaScript)</a></li><li><a href="/en-US/docs/Learn/Server-side/Express_Nodejs/Introduction">Express/Node introduction</a></li><li><a href="/en-US/docs/Learn/Server-side/Express_Nodejs/development_environment">Setting up a Node development environment</a></li><li><a href="/en-US/docs/Learn/Server-side/Express_Nodejs/Tutorial_local_library_website">Express Tutorial: The Local Library website</a></li><li><a href="/en-US/docs/Learn/Server-side/Express_Nodejs/skeleton_website">Express Tutorial Part 2: Creating a skeleton website</a></li><li><a href="/en-US/docs/Learn/Server-side/Express_Nodejs/mongoose">Express Tutorial Part 3: Using a Database (with Mongoose)</a></li><li><a href="/en-US/docs/Learn/Server-side/Express_Nodejs/routes">Express Tutorial Part 4: Routes and controllers</a></li><li><a href="/en-US/docs/Learn/Server-side/Express_Nodejs/Displaying_data">Express Tutorial Part 5: Displaying library data</a></li><li><a href="/en-US/docs/Learn/Server-side/Express_Nodejs/forms">Express Tutorial Part 6: Working with forms</a></li><li><a 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="/en-US/docs/Learn/Common_questions">Further resources</a></li><li><details open=""><summary>Common questions</summary><ol><li><a href="/en-US/docs/Learn/Common_questions">Common questions</a></li><li><a href="/en-US/docs/Learn/HTML/Howto">Use HTML to solve common problems</a></li><li><a href="/en-US/docs/Learn/CSS/Howto">Use CSS to solve common problems</a></li><li><em><a href="/en-US/docs/Learn/JavaScript/Howto" aria-current="page">Solve common problems in your JavaScript code</a></em></li><li><a href="/en-US/docs/Learn/Common_questions/Web_mechanics">Web mechanics</a></li><li><a href="/en-US/docs/Learn/Common_questions/Tools_and_setup">Tools and setup</a></li><li><a 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">In this article</h2></header><ul class="document-toc-list"><li class="document-toc-item "><a class="document-toc-link" href="#common_beginners_mistakes">Common beginner's mistakes</a></li><li class="document-toc-item "><a class="document-toc-link" href="#basic_definitions">Basic definitions</a></li><li class="document-toc-item "><a class="document-toc-link" href="#basic_use_cases">Basic use cases</a></li><li class="document-toc-item "><a class="document-toc-link" href="#intermediate_use_cases">Intermediate use cases</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="en-US"><header><h1>Solve common problems in your JavaScript code</h1></header><div class="section-content"><p>The following links point to solutions to common problems you may encounter when writing JavaScript.</p></div><section aria-labelledby="common_beginners_mistakes"><h2 id="common_beginners_mistakes"><a href="#common_beginners_mistakes">Common beginner's mistakes</a></h2><div class="section-content"></div></section><section aria-labelledby="correct_spelling_and_casing"><h3 id="correct_spelling_and_casing"><a href="#correct_spelling_and_casing">Correct spelling and casing</a></h3><div class="section-content"><p>If your code doesn't work and/or the browser complains that something is undefined, check that you've spelt all your variable names, function names, etc. correctly.</p> <p>Some common built-in browser functions that cause problems are:</p> <figure class="table-container"><table> <thead> <tr> <th>Correct</th> <th>Wrong</th> </tr> </thead> <tbody> <tr> <td><code>getElementsByTagName()</code></td> <td><code>getElementByTagName()</code></td> </tr> <tr> <td><code>getElementsByName()</code></td> <td><code>getElementByName()</code></td> </tr> <tr> <td><code>getElementsByClassName()</code></td> <td><code>getElementByClassName()</code></td> </tr> <tr> <td><code>getElementById()</code></td> <td><code>getElementsById()</code></td> </tr> </tbody> </table></figure></div></section><section aria-labelledby="semicolon_position"><h3 id="semicolon_position"><a href="#semicolon_position">Semicolon position</a></h3><div class="section-content"><p>You need to make sure you don't place any semicolons incorrectly. For example:</p> <figure class="table-container"><table> <thead> <tr> <th>Correct</th> <th>Wrong</th> </tr> </thead> <tbody> <tr> <td><code>elem.style.color = 'red';</code></td> <td><code>elem.style.color = 'red;'</code></td> </tr> </tbody> </table></figure></div></section><section aria-labelledby="functions"><h3 id="functions"><a href="#functions">Functions</a></h3><div class="section-content"><p>There are a number of things that can go wrong with functions.</p> <p>One of the most common errors is to declare the function, but not call it anywhere. For example:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>function myFunction() { alert("This is my function."); } </code></pre></div> <p>This code won't do anything unless you call it with the following statement:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>myFunction(); </code></pre></div> <h4 id="function_scope">Function scope</h4> <p>Remember that <a href="/en-US/docs/Learn/JavaScript/Building_blocks/Functions#function_scope_and_conflicts">functions have their own scope</a> — you can't access a variable value set inside a function from outside the function, unless you declared the variable globally (i.e. not inside any functions), or <a href="/en-US/docs/Learn/JavaScript/Building_blocks/Return_values">return the value</a> from the function.</p> <h4 id="running_code_after_a_return_statement">Running code after a return statement</h4> <p>Remember also that when you return from a function, the JavaScript interpreter exits the function — no code after the return statement will run.</p> <p>In fact, some browsers (like Firefox) will give you an error message in the developer console if you have code after a return statement. Firefox gives you "unreachable code after return statement".</p></div></section><section aria-labelledby="object_notation_versus_normal_assignment"><h3 id="object_notation_versus_normal_assignment"><a href="#object_notation_versus_normal_assignment">Object notation versus normal assignment</a></h3><div class="section-content"><p>When you assign something normally in JavaScript, you use a single equals sign, e.g.:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>const myNumber = 0; </code></pre></div> <p>With <a href="/en-US/docs/Learn/JavaScript/Objects">Objects</a>, however, you need to take care to use the correct syntax. The object must be surrounded by curly braces, member names must be separated from their values using colons, and members must be separated by commas. For example:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>const myObject = { name: "Chris", age: 38, }; </code></pre></div></div></section><section aria-labelledby="basic_definitions"><h2 id="basic_definitions"><a href="#basic_definitions">Basic definitions</a></h2><div class="section-content"><ul> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/What_is_JavaScript#a_high-level_definition">What is JavaScript?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Variables#what_is_a_variable">What is a variable?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Strings">What are strings?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Arrays#what_is_an_array">What is an array?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code">What is a loop?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Functions">What is a function?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Events">What is an event?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Objects/Basics#object_basics">What is an object?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Objects/JSON#no_really_what_is_json">What is JSON?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Introduction#what_are_apis">What is a web API?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Manipulating_documents#the_document_object_model">What is the DOM?</a></li> </ul></div></section><section aria-labelledby="basic_use_cases"><h2 id="basic_use_cases"><a href="#basic_use_cases">Basic use cases</a></h2><div class="section-content"></div></section><section aria-labelledby="general"><h3 id="general"><a href="#general">General</a></h3><div class="section-content"><ul> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/What_is_JavaScript#how_do_you_add_javascript_to_your_page">How do you add JavaScript to your page?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/What_is_JavaScript#comments">How do you add comments to JavaScript code?</a></li> </ul></div></section><section aria-labelledby="variables"><h3 id="variables"><a href="#variables">Variables</a></h3><div class="section-content"><ul> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Variables#declaring_a_variable">How do you declare a variable?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Variables#initializing_a_variable">How do you initialize a variable with a value?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Variables#updating_a_variable">How do you update a variable's value?</a> (also see <a href="/en-US/docs/Learn/JavaScript/First_steps/Math#assignment_operators">Assignment operators</a>)</li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Variables#variable_types">What data types can values have in JavaScript?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Variables#dynamic_typing">What does 'loosely typed' mean?</a></li> </ul></div></section><section aria-labelledby="math"><h3 id="math"><a href="#math">Math</a></h3><div class="section-content"><ul> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Math#types_of_numbers">What types of number do you have to deal with in web development?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Math#arithmetic_operators">How do you do basic math in JavaScript?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Math#operator_precedence">What is operator precedence, and how is it handled in JavaScript?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Math#increment_and_decrement_operators">How do you increment and decrement values in JavaScript?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Math#comparison_operators">How do you compare values in JavaScript?</a> (e.g. to see which one is bigger, or to see if one value is equal to another).</li> </ul></div></section><section aria-labelledby="strings"><h3 id="strings"><a href="#strings">Strings</a></h3><div class="section-content"><ul> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Strings#creating_a_string">How do you create a string in JavaScript?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Strings#single_quotes_vs._double_quotes">Do you have to use single quotes or double quotes?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Strings#escaping_characters_in_a_string">How do you escape characters in strings?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Strings#concatenating_strings">How do you join strings together?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Strings#numbers_vs._strings">Can you join strings and numbers together?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Useful_string_methods#finding_the_length_of_a_string">How do you find the length of a string?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Useful_string_methods#retrieving_a_specific_string_character">How do you find what character is at a certain position in a string?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Useful_string_methods#extracting_a_substring_from_a_string">How do you find and extract a specific substring from a string?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Useful_string_methods#changing_case">How do you change the case of a string?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Useful_string_methods#updating_parts_of_a_string">How do you replace one specific substring with another?</a></li> </ul></div></section><section aria-labelledby="arrays"><h3 id="arrays"><a href="#arrays">Arrays</a></h3><div class="section-content"><ul> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Arrays#creating_arrays">How do you create an array?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Arrays#accessing_and_modifying_array_items">How do you access and modify the items in an array?</a> (this includes multidimensional arrays)</li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Arrays#finding_the_length_of_an_array">How do you find the length of an array?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Arrays#adding_items">How do you add items to an array?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Arrays#removing_items">How do you remove items from an array?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Arrays#converting_between_strings_and_arrays">How do you split a string into array items, or join array items into a string?</a></li> </ul></div></section><section aria-labelledby="debugging_javascript"><h3 id="debugging_javascript"><a href="#debugging_javascript">Debugging JavaScript</a></h3><div class="section-content"><ul> <li><a href="/en-US/docs/Learn/JavaScript/First_steps/What_went_wrong#types_of_error">What are the basic types of error?</a></li> <li><a href="/en-US/docs/Learn/Common_questions/Tools_and_setup/What_are_browser_developer_tools">What are browser developer tools, and how do you access them?</a></li> <li><a href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/JavaScript#the_console_api">How do you log a value to the JavaScript console?</a></li> <li><a href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/JavaScript#using_the_javascript_debugger">How do you use breakpoints and other JavaScript debugging features?</a></li> </ul> <p>For more information on JavaScript debugging, see <a href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/JavaScript">Handling common JavaScript problems</a>. Also, see <a href="/en-US/docs/Learn/JavaScript/First_steps/What_went_wrong#other_common_errors">Other common errors</a> for a description of common errors.</p></div></section><section aria-labelledby="making_decisions_in_code"><h3 id="making_decisions_in_code"><a href="#making_decisions_in_code">Making decisions in code</a></h3><div class="section-content"><ul> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/conditionals">How do you execute different blocks of code, depending on a variable's value or other condition?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/conditionals#if...else_statements">How do you use if ...else statements?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/conditionals#nesting_if...else">How do you nest one decision block inside another?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/conditionals#logical_operators_and_or_and_not">How do you use AND, OR, and NOT operators in JavaScript?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/conditionals#switch_statements">How do you conveniently handle a large number of choices for one condition?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/conditionals#ternary_operator">How do you use a ternary operator to make a quick choice between two options based on a true or false test?</a></li> </ul></div></section><section aria-labelledby="loopingiteration"><h3 id="loopingiteration"><a href="#loopingiteration">Looping/iteration</a></h3><div class="section-content"><ul> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code">How do you run the same bit of code over and over again?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code#exiting_loops_with_break">How do you exit a loop before the end if a certain condition is met?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code#skipping_iterations_with_continue">How do you skip to the next iteration of a loop if a certain condition is met?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code#while_and_do_..._while">How do you use while and do...while loops?</a></li> </ul></div></section><section aria-labelledby="intermediate_use_cases"><h2 id="intermediate_use_cases"><a href="#intermediate_use_cases">Intermediate use cases</a></h2><div class="section-content"></div></section><section aria-labelledby="functions_2"><h3 id="functions_2"><a href="#functions_2">Functions</a></h3><div class="section-content"><ul> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Functions#built-in_browser_functions">How do you find functions in the browser?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Functions#functions_versus_methods">What is the difference between a function and a method?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Build_your_own_function">How do you create your own functions?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Functions#invoking_functions">How do you run (call, or invoke) a function?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Functions#anonymous_functions">What is an anonymous function?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Functions#function_parameters">How do you specify parameters (or arguments) when invoking a function?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Functions#function_scope_and_conflicts">What is function scope?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Return_values">What are return values, and how do you use them?</a></li> </ul></div></section><section aria-labelledby="objects"><h3 id="objects"><a href="#objects">Objects</a></h3><div class="section-content"><ul> <li><a href="/en-US/docs/Learn/JavaScript/Objects/Basics#object_basics">How do you create an object?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Objects/Basics#dot_notation">What is dot notation?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Objects/Basics#bracket_notation">What is bracket notation?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Objects/Basics#setting_object_members">How do you get and set the methods and properties of an object?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Objects/Basics#what_is_this">What is <code>this</code>, in the context of an object?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Objects/Classes_in_JavaScript#object-oriented_programming_from_10000_meters">What is object-oriented programming?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Objects/Classes_in_JavaScript#constructors_and_object_instances">What are constructors and instances, and how do you create them?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Objects/Classes_in_JavaScript#other_ways_to_create_object_instances">What different ways are there to create objects in JavaScript?</a></li> </ul></div></section><section aria-labelledby="json"><h3 id="json"><a href="#json">JSON</a></h3><div class="section-content"><ul> <li><a href="/en-US/docs/Learn/JavaScript/Objects/JSON#json_structure">How do you structure JSON data, and read it from JavaScript?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Objects/JSON#loading_our_json">How can you load a JSON file into a page?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Objects/JSON#converting_between_objects_and_text">How do you convert a JSON object to a text string, and back again?</a></li> </ul></div></section><section aria-labelledby="events"><h3 id="events"><a href="#events">Events</a></h3><div class="section-content"><ul> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Events#event_handler_properties">What are event handlers and how do you use them?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Events#inline_event_handlers_%e2%80%94_don%27t_use_these">What are inline event handlers?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Events#using_addeventlistener">What does the <code>addEventListener()</code> function do, and how do you use it?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Events#what_mechanism_should_i_use">Which mechanism should I use to add event code to my web pages?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Events#event_objects">What are event objects, and how do you use them?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Events#preventing_default_behavior">How do you prevent default event behavior?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Event_bubbling">How do events fire on nested elements? (event propagation, also related — event bubbling and capturing)</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Event_bubbling#event_delegation">What is event delegation, and how does it work?</a></li> </ul></div></section><section aria-labelledby="object-oriented_javascript"><h3 id="object-oriented_javascript"><a href="#object-oriented_javascript">Object-oriented JavaScript</a></h3><div class="section-content"><ul> <li><a href="/en-US/docs/Learn/JavaScript/Objects/Object_prototypes">What are object prototypes?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Objects/Object_prototypes#the_constructor_property">What is the constructor property, and how can you use it?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Objects/Object_prototypes#modifying_prototypes">How do you add methods to the constructor?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Objects/Classes_in_JavaScript">How do you create a new constructor that inherits its members from a parent constructor?</a></li> <li><a href="/en-US/docs/Learn/JavaScript/Objects/Classes_in_JavaScript#object_member_summary">When should you use inheritance in JavaScript?</a></li> </ul></div></section><section aria-labelledby="web_apis"><h3 id="web_apis"><a href="#web_apis">Web APIs</a></h3><div class="section-content"><ul> <li><a href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Manipulating_documents#active_learning_basic_dom_manipulation">How do you manipulate the DOM (e.g. adding or removing elements) using JavaScript?</a></li> </ul></div></section></article><aside class="article-footer"><div class="article-footer-inner"><div class="svg-container"><svg xmlns="http://www.w3.org/2000/svg" width="162" height="162" viewBox="0 0 162 162" fill="none" role="none"><mask id="b" fill="#fff"><path d="M97.203 47.04c8.113-7.886 18.004-13.871 28.906-17.492a78 78 0 0 1 33.969-3.39c11.443 1.39 22.401 5.295 32.024 11.411s17.656 14.28 23.476 23.86c5.819 9.579 9.269 20.318 10.083 31.385a69.85 69.85 0 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Metadata in HTML</a></li><li><a href=\"/en-US/docs/Learn/HTML/Introduction_to_HTML/HTML_text_fundamentals\">HTML text fundamentals</a></li><li><a href=\"/en-US/docs/Learn/HTML/Introduction_to_HTML/Creating_hyperlinks\">Creating hyperlinks</a></li><li><a href=\"/en-US/docs/Learn/HTML/Introduction_to_HTML/Advanced_text_formatting\">Advanced text formatting</a></li><li><a href=\"/en-US/docs/Learn/HTML/Introduction_to_HTML/Document_and_website_structure\">Document and website structure</a></li><li><a href=\"/en-US/docs/Learn/HTML/Introduction_to_HTML/Debugging_HTML\">Debugging HTML</a></li><li><a href=\"/en-US/docs/Learn/HTML/Introduction_to_HTML/Marking_up_a_letter\">Marking up a letter</a></li><li><a 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>Multimedia and embedding</summary><ol><li><a href=\"/en-US/docs/Learn/HTML/Multimedia_and_embedding\">Multimedia and embedding</a></li><li><a href=\"/en-US/docs/Learn/HTML/Multimedia_and_embedding/Images_in_HTML\">Images in HTML</a></li><li><a href=\"/en-US/docs/Learn/HTML/Multimedia_and_embedding/Video_and_audio_content\">Video and audio content</a></li><li><a href=\"/en-US/docs/Learn/HTML/Multimedia_and_embedding/Other_embedding_technologies\">From object to iframe — other embedding technologies</a></li><li><a href=\"/en-US/docs/Learn/HTML/Multimedia_and_embedding/Adding_vector_graphics_to_the_Web\">Adding vector graphics to the web</a></li><li><a href=\"/en-US/docs/Learn/HTML/Multimedia_and_embedding/Responsive_images\">Responsive images</a></li><li><a href=\"/en-US/docs/Learn/HTML/Multimedia_and_embedding/Mozilla_splash_page\">Mozilla splash page</a></li></ol></details></li><li><details><summary>HTML tables</summary><ol><li><a href=\"/en-US/docs/Learn/HTML/Tables\">HTML tables</a></li><li><a href=\"/en-US/docs/Learn/HTML/Tables/Basics\">HTML table basics</a></li><li><a href=\"/en-US/docs/Learn/HTML/Tables/Advanced\">HTML table advanced features and accessibility</a></li><li><a href=\"/en-US/docs/Learn/HTML/Tables/Structuring_planet_data\">Structuring planet data</a></li></ol></details></li><li class=\"section\"><a href=\"/en-US/docs/Learn/CSS\">CSS — Styling the web</a></li><li><details><summary>CSS first steps</summary><ol><li><a href=\"/en-US/docs/Learn/CSS/First_steps\">CSS first steps</a></li><li><a href=\"/en-US/docs/Learn/CSS/First_steps/What_is_CSS\">What is CSS?</a></li><li><a href=\"/en-US/docs/Learn/CSS/First_steps/Getting_started\">Getting started with CSS</a></li><li><a href=\"/en-US/docs/Learn/CSS/First_steps/How_CSS_is_structured\">How CSS is structured</a></li><li><a href=\"/en-US/docs/Learn/CSS/First_steps/How_CSS_works\">How CSS works</a></li><li><a href=\"/en-US/docs/Learn/CSS/First_steps/Styling_a_biography_page\">Styling a biography page</a></li></ol></details></li><li><details><summary>CSS building blocks</summary><ol><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks\">CSS building blocks</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Selectors\">CSS selectors</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Selectors/Type_Class_and_ID_Selectors\">Type, class, and ID selectors</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Selectors/Attribute_selectors\">Attribute selectors</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Selectors/Pseudo-classes_and_pseudo-elements\">Pseudo-classes and pseudo-elements</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Selectors/Combinators\">Combinators</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Cascade_and_inheritance\">Cascade, specificity, and inheritance</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Cascade_layers\">Cascade layers</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/The_box_model\">The box model</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Backgrounds_and_borders\">Backgrounds and borders</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Handling_different_text_directions\">Handling different text directions</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Overflowing_content\">Overflowing content</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Values_and_units\">CSS values and units</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Sizing_items_in_CSS\">Sizing items in CSS</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Images_media_form_elements\">Images, media, and form elements</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Styling_tables\">Styling tables</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Advanced_styling_effects\">Advanced styling effects</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Debugging_CSS\">Debugging CSS</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Organizing\">Organizing your CSS</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Fundamental_CSS_comprehension\">Fundamental CSS comprehension</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Creating_fancy_letterheaded_paper\">Creating fancy letterheaded paper</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/A_cool_looking_box\">A cool-looking box</a></li></ol></details></li><li><details><summary>Styling text</summary><ol><li><a href=\"/en-US/docs/Learn/CSS/Styling_text\">CSS styling text</a></li><li><a href=\"/en-US/docs/Learn/CSS/Styling_text/Fundamentals\">Fundamental text and font styling</a></li><li><a href=\"/en-US/docs/Learn/CSS/Styling_text/Styling_lists\">Styling lists</a></li><li><a href=\"/en-US/docs/Learn/CSS/Styling_text/Styling_links\">Styling links</a></li><li><a href=\"/en-US/docs/Learn/CSS/Styling_text/Web_fonts\">Web fonts</a></li><li><a href=\"/en-US/docs/Learn/CSS/Styling_text/Typesetting_a_homepage\">Typesetting a community school homepage</a></li></ol></details></li><li><details><summary>CSS layout</summary><ol><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout\">CSS layout</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Introduction\">Introduction to CSS layout</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Normal_Flow\">Normal Flow</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Flexbox\">Flexbox</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Grids\">Grids</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Floats\">Floats</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Positioning\">Positioning</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Multiple-column_Layout\">Multiple-column layout</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Responsive_Design\">Responsive design</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Media_queries\">Beginner's guide to media queries</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Legacy_Layout_Methods\">Legacy layout methods</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Supporting_Older_Browsers\">Supporting older browsers</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Fundamental_Layout_Comprehension\">Fundamental layout comprehension</a></li></ol></details></li><li class=\"section\"><a href=\"/en-US/docs/Learn/JavaScript\">JavaScript — Dynamic client-side scripting</a></li><li><details><summary>JavaScript first steps</summary><ol><li><a href=\"/en-US/docs/Learn/JavaScript/First_steps\">JavaScript first steps</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/What_is_JavaScript\">What is JavaScript?</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/A_first_splash\">A first splash into JavaScript</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/What_went_wrong\">What went wrong? Troubleshooting JavaScript</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Variables\">Storing the information you need — Variables</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Math\">Basic math in JavaScript — numbers and operators</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Strings\">Handling text — strings in JavaScript</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Useful_string_methods\">Useful string methods</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Arrays\">Arrays</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Silly_story_generator\">Silly story generator</a></li></ol></details></li><li><details><summary>JavaScript building blocks</summary><ol><li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks\">JavaScript building blocks</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/conditionals\">Making decisions in your code — conditionals</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code\">Looping code</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Functions\">Functions — reusable blocks of code</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Build_your_own_function\">Build your own function</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Return_values\">Function return values</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Events\">Introduction to events</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Event_bubbling\">Event bubbling</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Image_gallery\">Image gallery</a></li></ol></details></li><li><details><summary>Introducing JavaScript objects</summary><ol><li><a href=\"/en-US/docs/Learn/JavaScript/Objects\">Introducing JavaScript objects</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Basics\">JavaScript object basics</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Object_prototypes\">Object prototypes</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Object-oriented_programming\">Object-oriented programming</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Classes_in_JavaScript\">Classes in JavaScript</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Objects/JSON\">Working with JSON</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Object_building_practice\">Object building practice</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Adding_bouncing_balls_features\">Adding features to our bouncing balls demo</a></li></ol></details></li><li><details><summary>Asynchronous JavaScript</summary><ol><li><a href=\"/en-US/docs/Learn/JavaScript/Asynchronous\">Asynchronous JavaScript</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Asynchronous/Introducing\">Introducing asynchronous JavaScript</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Asynchronous/Promises\">How to use promises</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Asynchronous/Implementing_a_promise-based_API\">How to implement a promise-based API</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Asynchronous/Introducing_workers\">Introducing workers</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Asynchronous/Sequencing_animations\">Sequencing animations</a></li></ol></details></li><li><details><summary>Client-side web APIs</summary><ol><li><a href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs\">Client-side web APIs</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Introduction\">Introduction to web APIs</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Manipulating_documents\">Manipulating documents</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Fetching_data\">Fetching data from the server</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Third_party_APIs\">Third-party APIs</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Drawing_graphics\">Drawing graphics</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Video_and_audio_APIs\">Video and Audio APIs</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Client-side_storage\">Client-side storage</a></li></ol></details></li><li class=\"section\"><a href=\"/en-US/docs/Learn/Forms\">Web forms — Working with user data</a></li><li><details><summary>Web form building blocks</summary><ol><li><a href=\"/en-US/docs/Learn/Forms\">Web form building blocks</a></li><li><a href=\"/en-US/docs/Learn/Forms/Your_first_form\">Your first form</a></li><li><a href=\"/en-US/docs/Learn/Forms/How_to_structure_a_web_form\">How to structure a web form</a></li><li><a href=\"/en-US/docs/Learn/Forms/Basic_native_form_controls\">Basic native form controls</a></li><li><a href=\"/en-US/docs/Learn/Forms/HTML5_input_types\">The HTML5 input types</a></li><li><a href=\"/en-US/docs/Learn/Forms/Other_form_controls\">Other form controls</a></li><li><a href=\"/en-US/docs/Learn/Forms/Styling_web_forms\">Styling web forms</a></li><li><a href=\"/en-US/docs/Learn/Forms/Advanced_form_styling\">Advanced form styling</a></li><li><a href=\"/en-US/docs/Learn/Forms/UI_pseudo-classes\">UI pseudo-classes</a></li><li><a href=\"/en-US/docs/Learn/Forms/Form_validation\">Client-side form validation</a></li><li><a href=\"/en-US/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 href=\"/en-US/docs/Learn/Forms/How_to_build_custom_form_controls\">How to build custom form controls</a></li><li><a href=\"/en-US/docs/Learn/Forms/Sending_forms_through_JavaScript\">Sending forms through JavaScript</a></li><li><a href=\"/en-US/docs/Learn/Forms/Property_compatibility_table_for_form_controls\">CSS property compatibility table for form controls</a></li><li><a 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=\"/en-US/docs/Learn/Accessibility\">Accessibility — Make the web usable by everyone</a></li><li><details><summary>Accessibility guides</summary><ol><li><a href=\"/en-US/docs/Learn/Accessibility\">Accessibility</a></li><li><a href=\"/en-US/docs/Learn/Accessibility/What_is_accessibility\">What is accessibility?</a></li><li><a href=\"/en-US/docs/Learn/Accessibility/HTML\">HTML: A good basis for accessibility</a></li><li><a href=\"/en-US/docs/Learn/Accessibility/CSS_and_JavaScript\">CSS and JavaScript accessibility best practices</a></li><li><a href=\"/en-US/docs/Learn/Accessibility/WAI-ARIA_basics\">WAI-ARIA basics</a></li><li><a href=\"/en-US/docs/Learn/Accessibility/Multimedia\">Accessible multimedia</a></li><li><a href=\"/en-US/docs/Learn/Accessibility/Mobile\">Mobile accessibility</a></li><li><a href=\"/en-US/docs/Learn/Accessibility/Accessibility_troubleshooting\">Assessment: Accessibility troubleshooting</a></li></ol></details></li><li class=\"section\"><a href=\"/en-US/docs/Learn/Performance\">Performance — Making websites fast and responsive</a></li><li><details><summary>Performance guides</summary><ol><li><a href=\"/en-US/docs/Learn/Performance\">Web performance</a></li><li><a href=\"/en-US/docs/Learn/Performance/why_web_performance\">The \"why\" of web performance</a></li><li><a href=\"/en-US/docs/Learn/Performance/What_is_web_performance\">What is web performance?</a></li><li><a href=\"/en-US/docs/Learn/Performance/Perceived_performance\">Perceived performance</a></li><li><a href=\"/en-US/docs/Learn/Performance/Measuring_performance\">Measuring performance</a></li><li><a href=\"/en-US/docs/Learn/Performance/Multimedia\">Multimedia: Images</a></li><li><a href=\"/en-US/docs/Learn/Performance/video\">Multimedia: video</a></li><li><a href=\"/en-US/docs/Learn/Performance/JavaScript\">JavaScript performance optimization</a></li><li><a href=\"/en-US/docs/Learn/Performance/HTML\">HTML performance optimization</a></li><li><a href=\"/en-US/docs/Learn/Performance/CSS\">CSS performance optimization</a></li><li><a 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=\"/en-US/docs/Learn/MathML\">MathML — Writing mathematics with MathML</a></li><li><details><summary>MathML first steps</summary><ol><li><a href=\"/en-US/docs/Learn/MathML/First_steps\">MathML first steps</a></li><li><a href=\"/en-US/docs/Learn/MathML/First_steps/Getting_started\">Getting started with MathML</a></li><li><a href=\"/en-US/docs/Learn/MathML/First_steps/Text_containers\">MathML Text Containers</a></li><li><a href=\"/en-US/docs/Learn/MathML/First_steps/Fractions_and_roots\">MathML fractions and roots</a></li><li><a href=\"/en-US/docs/Learn/MathML/First_steps/Scripts\">MathML scripted elements</a></li><li><a href=\"/en-US/docs/Learn/MathML/First_steps/Tables\">MathML tables</a></li><li><a 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=\"/en-US/docs/Learn/../Games\">Games — Developing games for the web</a></li><li><details><summary>Guides and tutorials</summary><ol><li><a href=\"/en-US/docs/Games/Introduction\">Introduction to game development for the Web</a></li><li><a href=\"/en-US/docs/Games/Techniques\">Techniques for game development</a></li><li><a href=\"/en-US/docs/Games/Tutorials\">Tutorials</a></li><li><a href=\"/en-US/docs/Games/Publishing_games\">Publishing games</a></li></ol></details></li><li class=\"section\"><a href=\"/en-US/docs/Learn/Tools_and_testing\">Tools and testing</a></li><li><details><summary>Client-side web development tools</summary><ol><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools\">Understanding client-side web development tools</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Overview\">Client-side tooling overview</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Command_line\">Command line crash course</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Package_management\">Package management basics</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Introducing_complete_toolchain\">Introducing a complete toolchain</a></li><li><a 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 href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Introduction\">Introduction to client-side frameworks</a></li><li><a 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=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_getting_started\">Getting started with React</a></li><li><a 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 href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_components\">Componentizing our React app</a></li><li><a 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 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 href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_accessibility\">Accessibility in React</a></li><li><a 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 href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_getting_started\">Getting started with Ember</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_structure_componentization\">Ember app structure and componentization</a></li><li><a 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 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 href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_routing\">Routing in Ember</a></li><li><a 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=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_getting_started\">Getting started with Vue</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_first_component\">Creating our first Vue component</a></li><li><a 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 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 href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_styling\">Styling Vue components with CSS</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_computed_properties\">Using Vue computed properties</a></li><li><a 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 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 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 href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_getting_started\">Getting started with Svelte</a></li><li><a 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 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 href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_components\">Componentizing our Svelte app</a></li><li><a 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 href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_stores\">Working with Svelte stores</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_TypeScript\">TypeScript support in Svelte</a></li><li><a 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 href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_getting_started\">Getting started with Angular</a></li><li><a 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 href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_styling\">Styling our Angular app</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_item_component\">Creating an item component</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_filtering\">Filtering our to-do items</a></li><li><a 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 href=\"/en-US/docs/Learn/Tools_and_testing/GitHub\">Git and GitHub</a></li></ol></details></li><li><details><summary>Cross browser testing</summary><ol><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing\">Cross browser testing</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Introduction\">Introduction to cross-browser testing</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Testing_strategies\">Strategies for carrying out testing</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/HTML_and_CSS\">Handling common HTML and CSS problems</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/JavaScript\">Handling common JavaScript problems</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Accessibility\">Handling common accessibility problems</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Feature_detection\">Implementing feature detection</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Automated_testing\">Introduction to automated testing</a></li><li><a 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=\"/en-US/docs/Learn/Server-side\">Server-side website programming</a></li><li><details><summary>First steps</summary><ol><li><a href=\"/en-US/docs/Learn/Server-side/First_steps\">Server-side website programming first steps</a></li><li><a href=\"/en-US/docs/Learn/Server-side/First_steps/Introduction\">Introduction to the server side</a></li><li><a href=\"/en-US/docs/Learn/Server-side/First_steps/Client-Server_overview\">Client-Server Overview</a></li><li><a href=\"/en-US/docs/Learn/Server-side/First_steps/Web_frameworks\">Server-side web frameworks</a></li><li><a href=\"/en-US/docs/Learn/Server-side/First_steps/Website_security\">Website security</a></li></ol></details></li><li><details><summary>Django web framework (Python)</summary><ol><li><a href=\"/en-US/docs/Learn/Server-side/Django\">Django Web Framework (Python)</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Introduction\">Django introduction</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/development_environment\">Setting up a Django development environment</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Tutorial_local_library_website\">Django Tutorial: The Local Library website</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/skeleton_website\">Django Tutorial Part 2: Creating a skeleton website</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Models\">Django Tutorial Part 3: Using models</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Admin_site\">Django Tutorial Part 4: Django admin site</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Home_page\">Django Tutorial Part 5: Creating our home page</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Generic_views\">Django Tutorial Part 6: Generic list and detail views</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Sessions\">Django Tutorial Part 7: Sessions framework</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Authentication\">Django Tutorial Part 8: User authentication and permissions</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Forms\">Django Tutorial Part 9: Working with forms</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Testing\">Django Tutorial Part 10: Testing a Django web application</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Deployment\">Django Tutorial Part 11: Deploying Django to production</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/web_application_security\">Django web application security</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/django_assessment_blog\">Assessment: DIY Django mini blog</a></li></ol></details></li><li><details><summary>Express Web Framework (Node.js/JavaScript)</summary><ol><li><a href=\"/en-US/docs/Learn/Server-side/Express_Nodejs\">Express web framework (Node.js/JavaScript)</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/Introduction\">Express/Node introduction</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/development_environment\">Setting up a Node development environment</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/Tutorial_local_library_website\">Express Tutorial: The Local Library website</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/skeleton_website\">Express Tutorial Part 2: Creating a skeleton website</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/mongoose\">Express Tutorial Part 3: Using a Database (with Mongoose)</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/routes\">Express Tutorial Part 4: Routes and controllers</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/Displaying_data\">Express Tutorial Part 5: Displaying library data</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/forms\">Express Tutorial Part 6: Working with forms</a></li><li><a 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=\"/en-US/docs/Learn/Common_questions\">Further resources</a></li><li><details open=\"\"><summary>Common questions</summary><ol><li><a href=\"/en-US/docs/Learn/Common_questions\">Common questions</a></li><li><a href=\"/en-US/docs/Learn/HTML/Howto\">Use HTML to solve common problems</a></li><li><a href=\"/en-US/docs/Learn/CSS/Howto\">Use CSS to solve common problems</a></li><li><em><a href=\"/en-US/docs/Learn/JavaScript/Howto\" aria-current=\"page\">Solve common problems in your JavaScript code</a></em></li><li><a href=\"/en-US/docs/Learn/Common_questions/Web_mechanics\">Web mechanics</a></li><li><a href=\"/en-US/docs/Learn/Common_questions/Tools_and_setup\">Tools and setup</a></li><li><a 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":"<p>The following links point to solutions to common problems you may encounter when writing JavaScript.</p>"}},{"type":"prose","value":{"id":"common_beginners_mistakes","title":"Common beginner's mistakes","isH3":false,"content":""}},{"type":"prose","value":{"id":"correct_spelling_and_casing","title":"Correct spelling and casing","isH3":true,"content":"<p>If your code doesn't work and/or the browser complains that something is undefined, check that you've spelt all your variable names, function names, etc. correctly.</p>\n<p>Some common built-in browser functions that cause problems are:</p>\n<figure class=\"table-container\"><table>\n <thead>\n <tr>\n <th>Correct</th>\n <th>Wrong</th>\n </tr>\n </thead>\n <tbody>\n <tr>\n <td><code>getElementsByTagName()</code></td>\n <td><code>getElementByTagName()</code></td>\n </tr>\n <tr>\n <td><code>getElementsByName()</code></td>\n <td><code>getElementByName()</code></td>\n </tr>\n <tr>\n <td><code>getElementsByClassName()</code></td>\n <td><code>getElementByClassName()</code></td>\n </tr>\n <tr>\n <td><code>getElementById()</code></td>\n <td><code>getElementsById()</code></td>\n </tr>\n </tbody>\n</table></figure>"}},{"type":"prose","value":{"id":"semicolon_position","title":"Semicolon position","isH3":true,"content":"<p>You need to make sure you don't place any semicolons incorrectly. For example:</p>\n<figure class=\"table-container\"><table>\n <thead>\n <tr>\n <th>Correct</th>\n <th>Wrong</th>\n </tr>\n </thead>\n <tbody>\n <tr>\n <td><code>elem.style.color = 'red';</code></td>\n <td><code>elem.style.color = 'red;'</code></td>\n </tr>\n </tbody>\n</table></figure>"}},{"type":"prose","value":{"id":"functions","title":"Functions","isH3":true,"content":"<p>There are a number of things that can go wrong with functions.</p>\n<p>One of the most common errors is to declare the function, but not call it anywhere. For example:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>function myFunction() {\n alert(\"This is my function.\");\n}\n</code></pre></div>\n<p>This code won't do anything unless you call it with the following statement:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>myFunction();\n</code></pre></div>\n<h4 id=\"function_scope\">Function scope</h4>\n<p>Remember that <a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Functions#function_scope_and_conflicts\">functions have their own scope</a> — you can't access a variable value set inside a function from outside the function, unless you declared the variable globally (i.e. not inside any functions), or <a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Return_values\">return the value</a> from the function.</p>\n<h4 id=\"running_code_after_a_return_statement\">Running code after a return statement</h4>\n<p>Remember also that when you return from a function, the JavaScript interpreter exits the function — no code after the return statement will run.</p>\n<p>In fact, some browsers (like Firefox) will give you an error message in the developer console if you have code after a return statement. Firefox gives you \"unreachable code after return statement\".</p>"}},{"type":"prose","value":{"id":"object_notation_versus_normal_assignment","title":"Object notation versus normal assignment","isH3":true,"content":"<p>When you assign something normally in JavaScript, you use a single equals sign, e.g.:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>const myNumber = 0;\n</code></pre></div>\n<p>With <a href=\"/en-US/docs/Learn/JavaScript/Objects\">Objects</a>, however, you need to take care to use the correct syntax. The object must be surrounded by curly braces, member names must be separated from their values using colons, and members must be separated by commas. For example:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>const myObject = {\n name: \"Chris\",\n age: 38,\n};\n</code></pre></div>"}},{"type":"prose","value":{"id":"basic_definitions","title":"Basic definitions","isH3":false,"content":"<ul>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/What_is_JavaScript#a_high-level_definition\">What is JavaScript?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Variables#what_is_a_variable\">What is a variable?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Strings\">What are strings?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Arrays#what_is_an_array\">What is an array?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code\">What is a loop?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Functions\">What is a function?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Events\">What is an event?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Basics#object_basics\">What is an object?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Objects/JSON#no_really_what_is_json\">What is JSON?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Introduction#what_are_apis\">What is a web API?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Manipulating_documents#the_document_object_model\">What is the DOM?</a></li>\n</ul>"}},{"type":"prose","value":{"id":"basic_use_cases","title":"Basic use cases","isH3":false,"content":""}},{"type":"prose","value":{"id":"general","title":"General","isH3":true,"content":"<ul>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/What_is_JavaScript#how_do_you_add_javascript_to_your_page\">How do you add JavaScript to your page?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/What_is_JavaScript#comments\">How do you add comments to JavaScript code?</a></li>\n</ul>"}},{"type":"prose","value":{"id":"variables","title":"Variables","isH3":true,"content":"<ul>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Variables#declaring_a_variable\">How do you declare a variable?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Variables#initializing_a_variable\">How do you initialize a variable with a value?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Variables#updating_a_variable\">How do you update a variable's value?</a> (also see <a href=\"/en-US/docs/Learn/JavaScript/First_steps/Math#assignment_operators\">Assignment operators</a>)</li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Variables#variable_types\">What data types can values have in JavaScript?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Variables#dynamic_typing\">What does 'loosely typed' mean?</a></li>\n</ul>"}},{"type":"prose","value":{"id":"math","title":"Math","isH3":true,"content":"<ul>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Math#types_of_numbers\">What types of number do you have to deal with in web development?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Math#arithmetic_operators\">How do you do basic math in JavaScript?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Math#operator_precedence\">What is operator precedence, and how is it handled in JavaScript?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Math#increment_and_decrement_operators\">How do you increment and decrement values in JavaScript?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Math#comparison_operators\">How do you compare values in JavaScript?</a> (e.g. to see which one is bigger, or to see if one value is equal to another).</li>\n</ul>"}},{"type":"prose","value":{"id":"strings","title":"Strings","isH3":true,"content":"<ul>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Strings#creating_a_string\">How do you create a string in JavaScript?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Strings#single_quotes_vs._double_quotes\">Do you have to use single quotes or double quotes?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Strings#escaping_characters_in_a_string\">How do you escape characters in strings?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Strings#concatenating_strings\">How do you join strings together?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Strings#numbers_vs._strings\">Can you join strings and numbers together?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Useful_string_methods#finding_the_length_of_a_string\">How do you find the length of a string?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Useful_string_methods#retrieving_a_specific_string_character\">How do you find what character is at a certain position in a string?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Useful_string_methods#extracting_a_substring_from_a_string\">How do you find and extract a specific substring from a string?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Useful_string_methods#changing_case\">How do you change the case of a string?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Useful_string_methods#updating_parts_of_a_string\">How do you replace one specific substring with another?</a></li>\n</ul>"}},{"type":"prose","value":{"id":"arrays","title":"Arrays","isH3":true,"content":"<ul>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Arrays#creating_arrays\">How do you create an array?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Arrays#accessing_and_modifying_array_items\">How do you access and modify the items in an array?</a> (this includes multidimensional arrays)</li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Arrays#finding_the_length_of_an_array\">How do you find the length of an array?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Arrays#adding_items\">How do you add items to an array?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Arrays#removing_items\">How do you remove items from an array?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Arrays#converting_between_strings_and_arrays\">How do you split a string into array items, or join array items into a string?</a></li>\n</ul>"}},{"type":"prose","value":{"id":"debugging_javascript","title":"Debugging JavaScript","isH3":true,"content":"<ul>\n <li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/What_went_wrong#types_of_error\">What are the basic types of error?</a></li>\n <li><a href=\"/en-US/docs/Learn/Common_questions/Tools_and_setup/What_are_browser_developer_tools\">What are browser developer tools, and how do you access them?</a></li>\n <li><a href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/JavaScript#the_console_api\">How do you log a value to the JavaScript console?</a></li>\n <li><a href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/JavaScript#using_the_javascript_debugger\">How do you use breakpoints and other JavaScript debugging features?</a></li>\n</ul>\n<p>For more information on JavaScript debugging, see <a href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/JavaScript\">Handling common JavaScript problems</a>. Also, see <a href=\"/en-US/docs/Learn/JavaScript/First_steps/What_went_wrong#other_common_errors\">Other common errors</a> for a description of common errors.</p>"}},{"type":"prose","value":{"id":"making_decisions_in_code","title":"Making decisions in code","isH3":true,"content":"<ul>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/conditionals\">How do you execute different blocks of code, depending on a variable's value or other condition?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/conditionals#if...else_statements\">How do you use if ...else statements?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/conditionals#nesting_if...else\">How do you nest one decision block inside another?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/conditionals#logical_operators_and_or_and_not\">How do you use AND, OR, and NOT operators in JavaScript?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/conditionals#switch_statements\">How do you conveniently handle a large number of choices for one condition?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/conditionals#ternary_operator\">How do you use a ternary operator to make a quick choice between two options based on a true or false test?</a></li>\n</ul>"}},{"type":"prose","value":{"id":"loopingiteration","title":"Looping/iteration","isH3":true,"content":"<ul>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code\">How do you run the same bit of code over and over again?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code#exiting_loops_with_break\">How do you exit a loop before the end if a certain condition is met?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code#skipping_iterations_with_continue\">How do you skip to the next iteration of a loop if a certain condition is met?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code#while_and_do_..._while\">How do you use while and do...while loops?</a></li>\n</ul>"}},{"type":"prose","value":{"id":"intermediate_use_cases","title":"Intermediate use cases","isH3":false,"content":""}},{"type":"prose","value":{"id":"functions_2","title":"Functions","isH3":true,"content":"<ul>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Functions#built-in_browser_functions\">How do you find functions in the browser?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Functions#functions_versus_methods\">What is the difference between a function and a method?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Build_your_own_function\">How do you create your own functions?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Functions#invoking_functions\">How do you run (call, or invoke) a function?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Functions#anonymous_functions\">What is an anonymous function?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Functions#function_parameters\">How do you specify parameters (or arguments) when invoking a function?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Functions#function_scope_and_conflicts\">What is function scope?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Return_values\">What are return values, and how do you use them?</a></li>\n</ul>"}},{"type":"prose","value":{"id":"objects","title":"Objects","isH3":true,"content":"<ul>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Basics#object_basics\">How do you create an object?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Basics#dot_notation\">What is dot notation?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Basics#bracket_notation\">What is bracket notation?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Basics#setting_object_members\">How do you get and set the methods and properties of an object?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Basics#what_is_this\">What is <code>this</code>, in the context of an object?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Classes_in_JavaScript#object-oriented_programming_from_10000_meters\">What is object-oriented programming?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Classes_in_JavaScript#constructors_and_object_instances\">What are constructors and instances, and how do you create them?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Classes_in_JavaScript#other_ways_to_create_object_instances\">What different ways are there to create objects in JavaScript?</a></li>\n</ul>"}},{"type":"prose","value":{"id":"json","title":"JSON","isH3":true,"content":"<ul>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Objects/JSON#json_structure\">How do you structure JSON data, and read it from JavaScript?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Objects/JSON#loading_our_json\">How can you load a JSON file into a page?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Objects/JSON#converting_between_objects_and_text\">How do you convert a JSON object to a text string, and back again?</a></li>\n</ul>"}},{"type":"prose","value":{"id":"events","title":"Events","isH3":true,"content":"<ul>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Events#event_handler_properties\">What are event handlers and how do you use them?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Events#inline_event_handlers_%e2%80%94_don%27t_use_these\">What are inline event handlers?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Events#using_addeventlistener\">What does the <code>addEventListener()</code> function do, and how do you use it?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Events#what_mechanism_should_i_use\">Which mechanism should I use to add event code to my web pages?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Events#event_objects\">What are event objects, and how do you use them?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Events#preventing_default_behavior\">How do you prevent default event behavior?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Event_bubbling\">How do events fire on nested elements? (event propagation, also related — event bubbling and capturing)</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Event_bubbling#event_delegation\">What is event delegation, and how does it work?</a></li>\n</ul>"}},{"type":"prose","value":{"id":"object-oriented_javascript","title":"Object-oriented JavaScript","isH3":true,"content":"<ul>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Object_prototypes\">What are object prototypes?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Object_prototypes#the_constructor_property\">What is the constructor property, and how can you use it?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Object_prototypes#modifying_prototypes\">How do you add methods to the constructor?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Classes_in_JavaScript\">How do you create a new constructor that inherits its members from a parent constructor?</a></li>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Classes_in_JavaScript#object_member_summary\">When should you use inheritance in JavaScript?</a></li>\n</ul>"}},{"type":"prose","value":{"id":"web_apis","title":"Web APIs","isH3":true,"content":"<ul>\n <li><a href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Manipulating_documents#active_learning_basic_dom_manipulation\">How do you manipulate the DOM (e.g. adding or removing elements) using JavaScript?</a></li>\n</ul>"}}],"toc":[{"text":"Common beginner's mistakes","id":"common_beginners_mistakes"},{"text":"Basic definitions","id":"basic_definitions"},{"text":"Basic use cases","id":"basic_use_cases"},{"text":"Intermediate use cases","id":"intermediate_use_cases"}],"summary":"The following links point to solutions to common problems you may encounter when writing JavaScript.","popularity":0.002,"modified":"2024-07-01T02:48:11.000Z","other_translations":[{"locale":"de","title":"Lösen Sie häufige Probleme in Ihrem JavaScript-Code","native":"Deutsch"},{"locale":"es","title":"Resuelva problemas comunes en su código JavaScript","native":"Español"},{"locale":"ja","title":"JavaScript のコードのよくある問題を解決する","native":"日本語"},{"locale":"ko","title":"Solve common problems in your JavaScript code","native":"한국어"},{"locale":"pt-BR","title":"Solve common problems in your JavaScript code","native":"Português (do Brasil)"},{"locale":"ru","title":"Решите общие проблемы в вашем JavaScript-коде","native":"Русский"},{"locale":"zh-CN","title":"解决 JavaSctript 代码的常见问题","native":"中文 (简体)"},{"locale":"zh-TW","title":"JavaScript 解決常見的問題","native":"正體中文 (繁體)"}],"pageType":"landing-page","source":{"folder":"en-us/learn/javascript/howto","github_url":"https://github.com/mdn/content/blob/main/files/en-us/learn/javascript/howto/index.md","last_commit_url":"https://github.com/mdn/content/commit/c20c12fab32381b983b4148d712fda227d34e2bd","filename":"index.md"},"short_title":"Solve common problems in your JavaScript code","parents":[{"uri":"/en-US/docs/Learn","title":"Guides"},{"uri":"/en-US/docs/Learn/JavaScript","title":"JavaScript — Dynamic client-side scripting"},{"uri":"/en-US/docs/Learn/JavaScript/Howto","title":"Solve common problems in your JavaScript code"}],"pageTitle":"Solve common problems in your JavaScript code - Learn web development | MDN","noIndexing":false}}</script></body></html>