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sidebar</span></label><input id="sidebar-filter-input" autoComplete="off" class="sidebar-filter-input-field false" type="text" placeholder="Filter" value=""/><button type="button" class="button action has-icon clear-sidebar-filter-button"><span class="button-wrap"><span class="icon icon-cancel "></span><span class="visually-hidden">Clear filter input</span></span></button></div></section></header><div class="sidebar-inner-nav"><div class="in-nav-toc"><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="#adding_interactivity">Adding Interactivity</a></li><li class="document-toc-item "><a class="document-toc-link" href="#creating_todos">Creating todos</a></li><li class="document-toc-item "><a class="document-toc-link" href="#storing_todos_with_a_service">Storing Todos with a service</a></li><li class="document-toc-item "><a class="document-toc-link" href="#using_the_service_from_our_header_component">Using the service from our header component</a></li><li class="document-toc-item "><a class="document-toc-link" href="#displaying_our_todos">Displaying our todos</a></li><li class="document-toc-item "><a class="document-toc-link" href="#summary">Summary</a></li></ul></section></div></div><div class="sidebar-body"><ol><li class="section"><a href="/en-US/docs/Learn_web_development/Getting_started">Getting started modules</a></li><li class="toggle"><details><summary><a href="/en-US/docs/Learn_web_development/Getting_started/Environment_setup">Environment setup</a></summary><ol><li><a href="/en-US/docs/Learn_web_development/Getting_started/Environment_setup/Installing_software">Installing basic software</a></li><li><a href="/en-US/docs/Learn_web_development/Getting_started/Environment_setup/Browsing_the_web">Browsing the web</a></li><li><a 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href="/en-US/docs/Learn_web_development/Getting_started/Your_first_website/Adding_interactivity">JavaScript: Adding interactivity</a></li><li><a href="/en-US/docs/Learn_web_development/Getting_started/Your_first_website/Publishing_your_website">Publishing your website</a></li></ol></details></li><li class="toggle"><details><summary><a href="/en-US/docs/Learn_web_development/Getting_started/Web_standards">Web standards</a></summary><ol><li><a href="/en-US/docs/Learn_web_development/Getting_started/Web_standards/How_the_web_works">How the web works</a></li><li><a href="/en-US/docs/Learn_web_development/Getting_started/Web_standards/The_web_standards_model">The web standards model</a></li><li><a href="/en-US/docs/Learn_web_development/Getting_started/Web_standards/How_browsers_load_websites">How browsers load websites</a></li></ol></details></li><li class="toggle"><details><summary><a href="/en-US/docs/Learn_web_development/Getting_started/Soft_skills">Soft skills</a></summary><ol><li><a href="/en-US/docs/Learn_web_development/Getting_started/Soft_skills/Research_and_learning">Research and learning</a></li><li><a href="/en-US/docs/Learn_web_development/Getting_started/Soft_skills/Collaboration_and_teamwork">Collaboration and teamwork</a></li><li><a href="/en-US/docs/Learn_web_development/Getting_started/Soft_skills/Workflows_and_processes">Workflows and processes</a></li><li><a href="/en-US/docs/Learn_web_development/Getting_started/Soft_skills/Job_interviews">Succeeding in job interviews</a></li></ol></details></li><li class="section"><a href="/en-US/docs/Learn_web_development/Core">Core modules</a></li><li class="toggle"><details><summary><a href="/en-US/docs/Learn_web_development/Core/Structuring_content">Structuring content with HTML</a></summary><ol><li><a href="/en-US/docs/Learn_web_development/Core/Structuring_content/Basic_HTML_syntax">Basic HTML syntax</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Structuring_content/Webpage_metadata">What's in the head? Webpage metadata</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Structuring_content/Headings_and_paragraphs">Headings and paragraphs in HTML</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Structuring_content/Emphasis_and_importance">Emphasis and importance</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Structuring_content/Lists">Lists</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Structuring_content/Structuring_documents">Structuring documents</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Structuring_content/Advanced_text_features">Advanced text features</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Structuring_content/Creating_links">Creating links</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Structuring_content/Marking_up_a_letter">Challenge: Marking up a letter</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Structuring_content/Structuring_a_page_of_content">Challenge: Structuring a page of content</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Structuring_content/HTML_images">HTML images</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Structuring_content/HTML_video_and_audio">HTML video and audio</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Structuring_content/Mozilla_splash_page">Challenge: Mozilla splash page</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Structuring_content/HTML_table_basics">HTML table basics</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Structuring_content/Table_accessibility">HTML table accessibility</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Structuring_content/Planet_data_table">Challenge: Structuring a planet data table</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Structuring_content/HTML_forms">Forms and buttons in HTML</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Structuring_content/Debugging_HTML">Debugging HTML</a></li></ol></details></li><li class="toggle"><details><summary><a href="/en-US/docs/Learn_web_development/Core/Styling_basics">CSS styling basics</a></summary><ol><li><a href="/en-US/docs/Learn_web_development/Core/Styling_basics/What_is_CSS">What is CSS?</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Styling_basics/Getting_started">Getting started with CSS</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Styling_basics/Styling_a_bio_page">Challenge: Styling a biography page</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Styling_basics/Basic_selectors">Basic CSS selectors</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Styling_basics/Attribute_selectors">Attribute selectors</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Styling_basics/Pseudo_classes_and_elements">Pseudo-classes and pseudo-elements</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Styling_basics/Combinators">Combinators</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Styling_basics/Box_model">The box model</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Styling_basics/Handling_conflicts">Handling conflicts</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Styling_basics/Values_and_units">CSS values and units</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Styling_basics/Sizing">Sizing items in CSS</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Styling_basics/Backgrounds_and_borders">Backgrounds and borders</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Styling_basics/Overflow">Overflowing content</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Styling_basics/Images_media_forms">Images, media, and form elements</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Styling_basics/Tables">Styling tables</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Styling_basics/Debugging_CSS">Debugging CSS</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Styling_basics/Fundamental_CSS_comprehension">Challenge: Fundamental CSS comprehension</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Styling_basics/Fancy_letterheaded_paper">Challenge: Creating fancy letterheaded paper</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Styling_basics/Cool-looking_box">Challenge: A cool-looking box</a></li></ol></details></li><li class="toggle"><details><summary><a href="/en-US/docs/Learn_web_development/Core/Text_styling">CSS text styling</a></summary><ol><li><a href="/en-US/docs/Learn_web_development/Core/Text_styling/Fundamentals">Fundamental text and font styling</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Text_styling/Styling_lists">Styling lists</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Text_styling/Styling_links">Styling links</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Text_styling/Web_fonts">Web fonts</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Text_styling/Typesetting_a_homepage">Challenge: Typesetting a community school homepage</a></li></ol></details></li><li class="toggle"><details><summary><a href="/en-US/docs/Learn_web_development/Core/CSS_layout">CSS layout</a></summary><ol><li><a href="/en-US/docs/Learn_web_development/Core/CSS_layout/Introduction">Introduction to CSS layout</a></li><li><a href="/en-US/docs/Learn_web_development/Core/CSS_layout/Floats">Floats</a></li><li><a href="/en-US/docs/Learn_web_development/Core/CSS_layout/Positioning">Positioning</a></li><li><a href="/en-US/docs/Learn_web_development/Core/CSS_layout/Flexbox">Flexbox</a></li><li><a href="/en-US/docs/Learn_web_development/Core/CSS_layout/Grids">CSS grid layout</a></li><li><a href="/en-US/docs/Learn_web_development/Core/CSS_layout/Responsive_Design">Responsive design</a></li><li><a href="/en-US/docs/Learn_web_development/Core/CSS_layout/Media_queries">Media query fundamentals</a></li><li><a href="/en-US/docs/Learn_web_development/Core/CSS_layout/Fundamental_Layout_Comprehension">Challenge: Fundamental layout comprehension</a></li></ol></details></li><li class="toggle"><details><summary><a href="/en-US/docs/Learn_web_development/Core/Scripting">Dynamic scripting with JavaScript</a></summary><ol><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/What_is_JavaScript">What is JavaScript?</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/A_first_splash">A first splash into JavaScript</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/What_went_wrong">What went wrong? Troubleshooting JavaScript</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/Variables">Storing the information you need — Variables</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/Math">Basic math in JavaScript — numbers and operators</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/Strings">Handling text — strings in JavaScript</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/Useful_string_methods">Useful string methods</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/Arrays">Arrays</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/Silly_story_generator">Challenge: Silly story generator</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/Conditionals">Making decisions in your code — conditionals</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/Loops">Looping code</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/Functions">Functions — reusable blocks of code</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/Build_your_own_function">Build your own function</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/Return_values">Function return values</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/Events">Introduction to events</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/Event_bubbling">Event bubbling</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/Image_gallery">Challenge: Image gallery</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/Object_basics">JavaScript object basics</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/DOM_scripting">DOM scripting introduction</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/Network_requests">Making network requests with JavaScript</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/JSON">Working with JSON</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Scripting/Debugging_JavaScript">Debugging JavaScript and handling errors</a></li></ol></details></li><li class="toggle"><details><summary><a href="/en-US/docs/Learn_web_development/Core/Frameworks_libraries">JavaScript frameworks and libraries</a></summary><ol><li><a href="/en-US/docs/Learn_web_development/Core/Frameworks_libraries/Introduction">Introduction to client-side frameworks</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Frameworks_libraries/Main_features">Framework main features</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Frameworks_libraries/React_getting_started">Getting started with React</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Frameworks_libraries/React_todo_list_beginning">Beginning our React todo list</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Frameworks_libraries/React_components">Componentizing our React app</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Frameworks_libraries/React_interactivity_events_state">React interactivity: Events and state</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Frameworks_libraries/React_interactivity_filtering_conditional_rendering">React interactivity: Editing, filtering, conditional rendering</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Frameworks_libraries/React_accessibility">Accessibility in React</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Frameworks_libraries/React_resources">React resources</a></li></ol></details></li><li class="toggle"><details><summary><a href="/en-US/docs/Learn_web_development/Core/Accessibility">Accessibility</a></summary><ol><li><a href="/en-US/docs/Learn_web_development/Core/Accessibility/What_is_accessibility">What is accessibility?</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Accessibility/Tooling">Accessibility tooling and assistive technology</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Accessibility/HTML">HTML: A good basis for accessibility</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Accessibility/CSS_and_JavaScript">CSS and JavaScript accessibility best practices</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Accessibility/WAI-ARIA_basics">WAI-ARIA basics</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Accessibility/Multimedia">Accessible multimedia</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Accessibility/Mobile">Mobile accessibility</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Accessibility/Accessibility_troubleshooting">Challenge: Accessibility troubleshooting</a></li></ol></details></li><li><a href="/en-US/docs/Learn_web_development/Core/Design_for_developers">Design for developers</a></li><li><a href="/en-US/docs/Learn_web_development/Core/Version_control">Version control</a></li><li class="section"><a href="/en-US/docs/Learn_web_development/Extensions">Extension modules</a></li><li class="toggle"><details><summary><a href="/en-US/docs/Learn_web_development/Extensions/Advanced_JavaScript_objects">Advanced JavaScript objects</a></summary><ol><li><a href="/en-US/docs/Learn_web_development/Extensions/Advanced_JavaScript_objects/Object_prototypes">Object prototypes</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Advanced_JavaScript_objects/Object-oriented_programming">Object-oriented programming</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Advanced_JavaScript_objects/Classes_in_JavaScript">Classes in JavaScript</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Advanced_JavaScript_objects/Object_building_practice">Object building practice</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Advanced_JavaScript_objects/Adding_bouncing_balls_features">Challenge: Adding features to our bouncing balls demo</a></li></ol></details></li><li class="toggle"><details><summary><a href="/en-US/docs/Learn_web_development/Extensions/Client-side_APIs">Client-side web APIs</a></summary><ol><li><a href="/en-US/docs/Learn_web_development/Extensions/Client-side_APIs/Introduction">Introduction to web APIs</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Client-side_APIs/Video_and_audio_APIs">Video and Audio APIs</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Client-side_APIs/Drawing_graphics">Drawing graphics</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Client-side_APIs/Client-side_storage">Client-side storage</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Client-side_APIs/Third_party_APIs">Third-party APIs</a></li></ol></details></li><li 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form</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Forms/How_to_structure_a_web_form">How to structure a web form</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Forms/Basic_native_form_controls">Basic native form controls</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Forms/HTML5_input_types">The HTML5 input types</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Forms/Other_form_controls">Other form controls</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Forms/Styling_web_forms">Styling web forms</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Forms/Advanced_form_styling">Advanced form styling</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Forms/UI_pseudo-classes">UI pseudo-classes</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Forms/Form_validation">Client-side form validation</a></li><li><a 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href="/en-US/docs/Learn_web_development/Extensions/Performance/CSS">CSS performance optimization</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Performance/business_case_for_performance">The business case for web performance</a></li></ol></details></li><li class="toggle"><details><summary><a href="/en-US/docs/Learn_web_development/Extensions/Testing">Testing</a></summary><ol><li><a href="/en-US/docs/Learn_web_development/Extensions/Testing/Introduction">Introduction to cross-browser testing</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Testing/Testing_strategies">Strategies for carrying out testing</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Testing/HTML_and_CSS">Handling common HTML and CSS problems</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Testing/Feature_detection">Implementing feature detection</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Testing/Automated_testing">Introduction to automated testing</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Testing/Your_own_automation_environment">Setting up your own test automation environment</a></li></ol></details></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Transform_animate">Transform and animate CSS</a></li><li><a href="/en-US/docs/Learn_web_development/Extensions/Security_privacy">Security and privacy</a></li><li class="section">Further resources</li><li class="toggle"><details><summary><a href="/en-US/docs/Learn_web_development/Howto">How to solve common problems</a></summary><ol><li><a href="/en-US/docs/Learn_web_development/Howto/Solve_HTML_problems">Solve common HTML problems</a></li><li><a href="/en-US/docs/Learn_web_development/Howto/Solve_CSS_problems">Solve common CSS problems</a></li><li><a href="/en-US/docs/Learn_web_development/Howto/Solve_JavaScript_problems">Solve common JavaScript problems</a></li><li><a href="/en-US/docs/Learn_web_development/Howto/Web_mechanics">Web mechanics</a></li><li><a href="/en-US/docs/Learn_web_development/Howto/Tools_and_setup">Tools and setup</a></li><li><a href="/en-US/docs/Learn_web_development/Howto/Design_and_accessibility">Design and accessibility</a></li></ol></details></li><li><a href="/en-US/docs/Learn_web_development/About">About</a></li><li><a href="/en-US/docs/Learn_web_development/Educators">Resources for educators</a></li><li><a href="/en-US/docs/Learn_web_development/Changelog">Changelog</a></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="#adding_interactivity">Adding Interactivity</a></li><li class="document-toc-item "><a class="document-toc-link" href="#creating_todos">Creating todos</a></li><li class="document-toc-item "><a class="document-toc-link" href="#storing_todos_with_a_service">Storing Todos with a service</a></li><li class="document-toc-item "><a class="document-toc-link" href="#using_the_service_from_our_header_component">Using the service from our header component</a></li><li class="document-toc-item "><a class="document-toc-link" href="#displaying_our_todos">Displaying our todos</a></li><li class="document-toc-item "><a class="document-toc-link" href="#summary">Summary</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>Ember interactivity: Events, classes and state</h1></header><div class="section-content"><ul class="prev-next"><li><a class="button secondary" href="/en-US/docs/Learn_web_development/Core/Frameworks_libraries/Ember_structure_componentization"><span class="button-wrap"> Previous </span></a></li><li><a class="button secondary" href="/en-US/docs/Learn_web_development/Core/Frameworks_libraries"><span class="button-wrap"> Overview: JavaScript frameworks and libraries</span></a></li><li><a class="button secondary" href="/en-US/docs/Learn_web_development/Core/Frameworks_libraries/Ember_conditional_footer"><span class="button-wrap"> Next </span></a></li></ul> <p>At this point we'll start adding some interactivity to our app, providing the ability to add and display new todo items. Along the way, we'll look at using events in Ember, creating component classes to contain JavaScript code to control interactive features, and setting up a service to keep track of the data state of our app.</p> <figure class="table-container"><table> <tbody> <tr> <th scope="row">Prerequisites:</th> <td> <p> At minimum, it is recommended that you are familiar with the core <a href="/en-US/docs/Learn_web_development/Core/Structuring_content">HTML</a>, <a href="/en-US/docs/Learn_web_development/Core/Styling_basics">CSS</a>, and <a href="/en-US/docs/Learn_web_development/Core/Scripting">JavaScript</a> languages, and have knowledge of the <a href="/en-US/docs/Learn_web_development/Getting_started/Environment_setup/Command_line">terminal/command line</a>. </p> <p> A deeper understanding of modern JavaScript features (such as classes, modules, etc.), will be extremely beneficial, as Ember makes heavy use of them. </p> </td> </tr> <tr> <th scope="row">Objective:</th> <td> To learn how to create component classes and use events to control interactivity, and keep track of app state using a service. </td> </tr> </tbody> </table></figure></div><section aria-labelledby="adding_interactivity"><h2 id="adding_interactivity"><a href="#adding_interactivity">Adding Interactivity</a></h2><div class="section-content"><p>Now we've got a refactored componentized version of our todo app, lets walk through how we can add the interactivity we need to make the app functional.</p> <p>When beginning to think about interactivity, it's good to declare what each component's goals and responsibilities are. In the below sections we'll do this for each component, and then walk you through how the functionality can be implemented.</p></div></section><section aria-labelledby="creating_todos"><h2 id="creating_todos"><a href="#creating_todos">Creating todos</a></h2><div class="section-content"><p>For our card-header / todo input, we'll want to be able to submit our typed in todo task when we press the <kbd>Enter</kbd> key and have it appear in the todos list.</p> <p>We want to be able to capture the text typed into the input. We do this so that our JavaScript code knows what we typed in, and we can save our todo and pass that text along to the todo list component to display.</p> <p>We can capture the <a href="/en-US/docs/Web/API/Element/keydown_event"><code>keydown</code></a> event via the <a href="https://api.emberjs.com/ember/3.16/classes/Ember.Templates.helpers/methods/on?anchor=on" class="external" target="_blank">on modifier</a>, which is just Ember syntactic sugar around <a href="/en-US/docs/Web/API/EventTarget/addEventListener"><code>addEventListener</code></a> and <a href="/en-US/docs/Web/API/EventTarget/removeEventListener"><code>removeEventListener</code></a> (see <a href="/en-US/docs/Learn_web_development/Core/Scripting/Events">Introduction to events</a> if needed).</p> <p>Add the new line shown below to your <code>header.hbs</code> file:</p> <div class="code-example"><div class="example-header"><span class="language-name">hbs</span></div><pre class="brush: hbs notranslate"><code><input class='new-todo' aria-label='What needs to be done?' placeholder='What needs to be done?' autofocus {{on 'keydown' this.onKeyDown}} > </code></pre></div> <p>This new attribute is inside double curly braces, which tells you it is part of Ember's dynamic templating syntax. The first argument passed to <code>on</code> is the type of event to respond to (<code>keydown</code>), and the last argument is the event handler — the code that will run in response to the <code>keydown</code> event firing. As you may expect from dealing with <a href="/en-US/docs/Learn_web_development/Core/Scripting/Object_basics#what_is_this">vanilla JavaScript objects</a>, the <code>this</code> keyword refers to the "context" or "scope" of the component. One component's <code>this</code> will be different from another component's <code>this</code>.</p> <p>We can define what is available inside <code>this</code> by generating a component class to go along with your component. This is a vanilla JavaScript class and has no special meaning to Ember, other than <em>extending</em> from the <code>Component</code> super-class.</p> <p>To create a header class to go with your header component, type this in to your terminal:</p> <div class="code-example"><div class="example-header"><span class="language-name">bash</span></div><pre class="brush: bash notranslate"><code>ember generate component-class header </code></pre></div> <p>This will create the following empty class file — <code>todomvc/app/components/header.js</code>:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>import Component from "@glimmer/component"; export default class HeaderComponent extends Component {} </code></pre></div> <p>Inside this file we will implement the event handler code. Update the content to the following:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>import Component from "@glimmer/component"; import { action } from "@ember/object"; export default class HeaderComponent extends Component { @action onKeyDown({ target, key }) { let text = target.value.trim(); let hasValue = Boolean(text); if (key === "Enter" && hasValue) { alert(text); target.value = ""; } } } </code></pre></div> <p>The <code>@action</code> decorator is the only Ember-specific code here (aside from extending from the <code>Component</code> superclass, and the Ember-specific items we are importing using <a href="/en-US/docs/Web/JavaScript/Guide/Modules">JavaScript module syntax</a>) — the rest of the file is vanilla JavaScript, and would work in any application. The <code>@action</code> decorator declares that the function is an "action", meaning it's a type of function that will be invoked from an event that occurred in the template. <code>@action</code> also binds the <code>this</code> of the function to the class instance.</p> <div class="notecard note"> <p><strong>Note:</strong> A decorator is basically a wrapper function, which wraps and calls other functions or properties, providing additional functionality along the way. For example, the <code>@tracked</code> decorator (see slightly later on) runs code it is applied to, but additionally tracks it and automatically updates the app when values change. <a href="https://www.sitepoint.com/javascript-decorators-what-they-are/" class="external" target="_blank">Read JavaScript Decorators: What They Are and When to Use Them</a> for more general information on decorators.</p> </div> <p>Coming back to our browser tab with the app running, we can type whatever we want, and when we hit <kbd>Enter</kbd> we'll be greeted with an alert message telling us exactly what we typed.</p> <p><img src="/en-US/docs/Learn_web_development/Core/Frameworks_libraries/Ember_interactivity_events_state/todos-hello-there-alert.png" alt="the initial placeholder state of the add function, showing the text entered into the input elements being alerted back to you." width="739" height="676" loading="lazy"></p> <p>With the interactivity of the header input out of the way, we need a place to store todos so that other components can access them.</p></div></section><section aria-labelledby="storing_todos_with_a_service"><h2 id="storing_todos_with_a_service"><a href="#storing_todos_with_a_service">Storing Todos with a service</a></h2><div class="section-content"><p>Ember has built-in application-level <strong>state</strong> management that we can use to manage the storage of our todos and allow each of our components to access data from that application-level state. Ember calls these constructs <a href="https://guides.emberjs.com/release/services/" class="external" target="_blank">Services</a>, and they live for the entire lifetime of the page (a page refresh will clear them; persisting the data for longer is beyond the scope of this tutorial).</p> <p>Run this terminal command to generate a service for us to store our todo-list data in:</p> <div class="code-example"><div class="example-header"><span class="language-name">bash</span></div><pre class="brush: bash notranslate"><code>ember generate service todo-data </code></pre></div> <p>This should give you a terminal output like so:</p> <pre class="brush: plain notranslate">installing service create app/services/todo-data.js installing service-test create tests/unit/services/todo-data-test.js </pre> <p>This creates a <code>todo-data.js</code> file inside the <code>todomvc/app/services</code> directory to contain our service, which initially contains an import statement and an empty class:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>import Service from "@ember/service"; export default class TodoDataService extends Service {} </code></pre></div> <p>First of all, we want to define <em>what a todo is</em>. We know that we want to track both the text of a todo, and whether or not it is completed.</p> <p>Add the following <code>import</code> statement below the existing one:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>import { tracked } from "@glimmer/tracking"; </code></pre></div> <p>Now add the following class below the previous line you added:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>class Todo { @tracked text = ""; @tracked isCompleted = false; constructor(text) { this.text = text; } } </code></pre></div> <p>This class represents a todo — it contains a <code>@tracked text</code> property containing the text of the todo, and a <code>@tracked isCompleted</code> property that specifies whether the todo has been completed or not. When instantiated, a <code>Todo</code> object will have an initial <code>text</code> value equal to the text given to it when created (see below), and an <code>isCompleted</code> value of <code>false</code>. The only Ember-specific part of this class is the <code>@tracked</code> decorator — this hooks in to the reactivity system and allows Ember to update what you're seeing in your app automatically if the tracked properties change. <a href="https://api.emberjs.com/ember/3.15/functions/@glimmer%2Ftracking/tracked" class="external" target="_blank">More information on tracked can be found here</a>.</p> <p>Now it's time to add to the body of the service.</p> <p>First add another <code>import</code> statement below the previous one, to make actions available inside the service:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>import { action } from "@ember/object"; </code></pre></div> <p>Update the existing <code>export default class TodoDataService extends Service { }</code> block as follows:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>export default class TodoDataService extends Service { @tracked todos = []; @action add(text) { let newTodo = new Todo(text); this.todos = [...this.todos, newTodo]; } } </code></pre></div> <p>Here, the <code>todos</code> property on the service will maintain our list of todos contained inside an array, and we'll mark it with <code>@tracked</code>, because when the value of <code>todos</code> is updated we want the UI to update as well.</p> <p>And just like before, the <code>add()</code> function that will be called from the template gets annotated with the <code>@action</code> decorator to bind it to the class instance. We <a href="/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax">spread our <code>todos</code> array</a> to add <code>newTodo</code> to it, which creates a new array and will trigger the reactivity system to update the UI.</p></div></section><section aria-labelledby="using_the_service_from_our_header_component"><h2 id="using_the_service_from_our_header_component"><a href="#using_the_service_from_our_header_component">Using the service from our header component</a></h2><div class="section-content"><p>Now that we've defined a way to add todos, we can interact with this service from the <code>header.js</code> input component to actually start adding them.</p> <p>First of all, the service needs to be injected into the template via the <code>@inject</code> decorator, which we'll rename to <code>@service</code> for semantic clarity. To do this, add the following <code>import</code> line to <code>header.js</code>, beneath the two existing <code>import</code> lines:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>import { inject as service } from "@ember/service"; </code></pre></div> <p>With this import in place, we can now make the <code>todo-data</code> service available inside the <code>HeaderComponent</code> class via the <code>todos</code> object, using the <code>@service</code> decorator. Add the following line just below the opening <code>export…</code> line:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>@service('todo-data') todos; </code></pre></div> <p>Now the placeholder <code>alert(text);</code> line can be replaced with a call to our new <code>add()</code> function. Replace it with the following:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>this.todos.add(text); </code></pre></div> <p>If we try this out in the todo app in our browser (<code>npm start</code>, go to <code>localhost:4200</code>), it will look like nothing happens after hitting the <kbd>Enter</kbd> key (although the fact that the app builds without any errors is a good sign). Using the <a href="https://guides.emberjs.com/release/ember-inspector/installation/" class="external" target="_blank">Ember Inspector</a> however, we can see that our todo was added:</p> <p><img src="/en-US/docs/Learn_web_development/Core/Frameworks_libraries/Ember_interactivity_events_state/todos-in-ember-inspector.gif" alt="The app being shown in the Ember inspector, to prove that added todos are being stored by the service, even if they are not being displayed in the UI yet" width="736" height="606" loading="lazy"></p></div></section><section aria-labelledby="displaying_our_todos"><h2 id="displaying_our_todos"><a href="#displaying_our_todos">Displaying our todos</a></h2><div class="section-content"><p>Now that we know that we can create todos, there needs to be a way to swap out our static "Buy Movie Tickets" todos with the todos we're actually creating. In the <code>TodoList</code> component, we'll want to get the todos out of the service, and render a <code>Todo</code> component for each todo.</p> <p>In order to retrieve the todos from the service, our <code>TodoList</code> component first needs a backing component class to contain this functionality. Press <kbd>Ctrl</kbd> + <kbd>C</kbd> to stop the development server, and enter the following terminal command:</p> <div class="code-example"><div class="example-header"><span class="language-name">bash</span></div><pre class="brush: bash notranslate"><code>ember generate component-class todo-list </code></pre></div> <p>This generates the new component class <code>todomvc/app/components/todo-list.js</code>.</p> <p>Populate this file with the following code, which exposes the <code>todo-data</code> service, via the <code>todos</code> property, to our template. This makes it accessible via <code>this.todos</code> inside both the class and the template:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>import Component from "@glimmer/component"; import { inject as service } from "@ember/service"; export default class TodoListComponent extends Component { @service("todo-data") todos; } </code></pre></div> <p>One issue here is that our service is called <code>todos</code>, but the list of todos is also called <code>todos</code>, so currently we would access the data using <code>this.todos.todos</code>. This is not intuitive, so we'll add a <a href="/en-US/docs/Web/JavaScript/Reference/Functions/get">getter</a> to the <code>todos</code> service called <code>all</code>, which will represent all todos.</p> <p>To do this, go back to your <code>todo-data.js</code> file and add the following below the <code>@tracked todos = [];</code> line:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>get all() { return this.todos; } </code></pre></div> <p>Now we can access the data using <code>this.todos.all</code>, which is much more intuitive. To put this in action, go to your <code>todo-list.hbs</code> component, and replace the static component calls:</p> <div class="code-example"><div class="example-header"><span class="language-name">hbs</span></div><pre class="brush: hbs notranslate"><code><Todo /> <Todo /> </code></pre></div> <p>With a dynamic <code>#each</code> block (which is basically syntactic sugar over the top of JavaScript's <a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach"><code>forEach()</code></a>) that creates a <code><Todo /></code> component for each todo available in the list of todos returned by the service's <code>all()</code> getter:</p> <div class="code-example"><div class="example-header"><span class="language-name">hbs</span></div><pre class="brush: hbs notranslate"><code>{{#each this.todos.all as |todo|}} <Todo @todo={{todo}} /> {{/each}} </code></pre></div> <p>Another way to look at this:</p> <ul> <li><code>this</code> — the rendering context / component instance.</li> <li><code>todos</code> — a property on <code>this</code>, which we defined in the <code>todo-list.js</code> component using <code>@service('todo-data') todos;</code>. This is a reference to the <code>todo-data</code> service, allowing us to interact with the service instance directly.</li> <li><code>all</code> — a getter on the <code>todo-data</code> service that returns all the todos.</li> </ul> <p>Try starting the server again and navigating to our app, and you'll find that it works! Well, sort of. Whenever you enter a new Todo item, a new list item appears below the text input, but unfortunately it always says "Buy Movie Tickets".</p> <p>This is because the text label inside each list item is hardcoded to that text, as seen in <code>todo.hbs</code>:</p> <div class="code-example"><div class="example-header"><span class="language-name">hbs</span></div><pre class="brush: hbs notranslate"><code><label>Buy Movie Tickets</label> </code></pre></div> <p>Update this line to use the Argument <code>@todo</code> — which will represent the Todo that we passed in to this component when it was invoked in <code>todo-list.hbs</code>, in the line <code><Todo @todo={{todo}} /></code>:</p> <div class="code-example"><div class="example-header"><span class="language-name">hbs</span></div><pre class="brush: hbs notranslate"><code><label>{{@todo.text}}</label> </code></pre></div> <p>OK, try it again. You should find that now the text submitted in the <code><input></code> is properly reflected in the UI:</p> <p><img src="/en-US/docs/Learn_web_development/Core/Frameworks_libraries/Ember_interactivity_events_state/todos-being-appended-with-correct-text.gif" alt="The app being shown in its final state of this article, with entered todo items being shown in the UI" width="849" height="662" loading="lazy"></p></div></section><section aria-labelledby="summary"><h2 id="summary"><a href="#summary">Summary</a></h2><div class="section-content"><p>OK, so that's great progress for now. We can now add todo items to our app, and the state of the data is tracked using our service. Next we'll move on to getting our footer functionality working, including the todo counter, and look at conditional rendering, including correctly styling todos when they've been checked. 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content are ©1998–2025 by individual mozilla.org contributors. Content available under <a href="/en-US/docs/MDN/Writing_guidelines/Attrib_copyright_license">a Creative Commons license</a>.</p></div></div></footer></div><script type="application/json" id="hydration">{"url":"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/Ember_interactivity_events_state","doc":{"body":[{"type":"prose","value":{"id":null,"title":null,"isH3":false,"content":"<ul class=\"prev-next\"><li><a class=\"button secondary\" href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/Ember_structure_componentization\"><span class=\"button-wrap\"> Previous </span></a></li><li><a class=\"button secondary\" href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries\"><span class=\"button-wrap\"> Overview: JavaScript frameworks and libraries</span></a></li><li><a class=\"button secondary\" href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/Ember_conditional_footer\"><span class=\"button-wrap\"> Next </span></a></li></ul>\n<p>At this point we'll start adding some interactivity to our app, providing the ability to add and display new todo items. Along the way, we'll look at using events in Ember, creating component classes to contain JavaScript code to control interactive features, and setting up a service to keep track of the data state of our app.</p>\n<figure class=\"table-container\"><table>\n <tbody>\n <tr>\n <th scope=\"row\">Prerequisites:</th>\n <td>\n <p>\n At minimum, it is recommended that you are familiar with the core\n <a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content\">HTML</a>,\n <a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics\">CSS</a>, and\n <a href=\"/en-US/docs/Learn_web_development/Core/Scripting\">JavaScript</a> languages, and\n have knowledge of the\n <a href=\"/en-US/docs/Learn_web_development/Getting_started/Environment_setup/Command_line\">terminal/command line</a>.\n </p>\n <p>\n A deeper understanding of modern JavaScript features (such as classes,\n modules, etc.), will be extremely beneficial, as Ember makes heavy use\n of them.\n </p>\n </td>\n </tr>\n <tr>\n <th scope=\"row\">Objective:</th>\n <td>\n To learn how to create component classes and use events to control\n interactivity, and keep track of app state using a service.\n </td>\n </tr>\n </tbody>\n</table></figure>"}},{"type":"prose","value":{"id":"adding_interactivity","title":"Adding Interactivity","isH3":false,"content":"<p>Now we've got a refactored componentized version of our todo app, lets walk through how we can add the interactivity we need to make the app functional.</p>\n<p>When beginning to think about interactivity, it's good to declare what each component's goals and responsibilities are. In the below sections we'll do this for each component, and then walk you through how the functionality can be implemented.</p>"}},{"type":"prose","value":{"id":"creating_todos","title":"Creating todos","isH3":false,"content":"<p>For our card-header / todo input, we'll want to be able to submit our typed in todo task when we press the <kbd>Enter</kbd> key and have it appear in the todos list.</p>\n<p>We want to be able to capture the text typed into the input. We do this so that our JavaScript code knows what we typed in, and we can save our todo and pass that text along to the todo list component to display.</p>\n<p>We can capture the <a href=\"/en-US/docs/Web/API/Element/keydown_event\"><code>keydown</code></a> event via the <a href=\"https://api.emberjs.com/ember/3.16/classes/Ember.Templates.helpers/methods/on?anchor=on\" class=\"external\" target=\"_blank\">on modifier</a>, which is just Ember syntactic sugar around <a href=\"/en-US/docs/Web/API/EventTarget/addEventListener\"><code>addEventListener</code></a> and <a href=\"/en-US/docs/Web/API/EventTarget/removeEventListener\"><code>removeEventListener</code></a> (see <a href=\"/en-US/docs/Learn_web_development/Core/Scripting/Events\">Introduction to events</a> if needed).</p>\n<p>Add the new line shown below to your <code>header.hbs</code> file:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">hbs</span></div><pre class=\"brush: hbs notranslate\"><code><input\n class='new-todo'\n aria-label='What needs to be done?'\n placeholder='What needs to be done?'\n autofocus\n {{on 'keydown' this.onKeyDown}}\n>\n</code></pre></div>\n<p>This new attribute is inside double curly braces, which tells you it is part of Ember's dynamic templating syntax. The first argument passed to <code>on</code> is the type of event to respond to (<code>keydown</code>), and the last argument is the event handler — the code that will run in response to the <code>keydown</code> event firing. As you may expect from dealing with <a href=\"/en-US/docs/Learn_web_development/Core/Scripting/Object_basics#what_is_this\">vanilla JavaScript objects</a>, the <code>this</code> keyword refers to the \"context\" or \"scope\" of the component. One component's <code>this</code> will be different from another component's <code>this</code>.</p>\n<p>We can define what is available inside <code>this</code> by generating a component class to go along with your component. This is a vanilla JavaScript class and has no special meaning to Ember, other than <em>extending</em> from the <code>Component</code> super-class.</p>\n<p>To create a header class to go with your header component, type this in to your terminal:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">bash</span></div><pre class=\"brush: bash notranslate\"><code>ember generate component-class header\n</code></pre></div>\n<p>This will create the following empty class file — <code>todomvc/app/components/header.js</code>:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>import Component from \"@glimmer/component\";\n\nexport default class HeaderComponent extends Component {}\n</code></pre></div>\n<p>Inside this file we will implement the event handler code. Update the content to the following:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>import Component from \"@glimmer/component\";\nimport { action } from \"@ember/object\";\n\nexport default class HeaderComponent extends Component {\n @action\n onKeyDown({ target, key }) {\n let text = target.value.trim();\n let hasValue = Boolean(text);\n\n if (key === \"Enter\" && hasValue) {\n alert(text);\n\n target.value = \"\";\n }\n }\n}\n</code></pre></div>\n<p>The <code>@action</code> decorator is the only Ember-specific code here (aside from extending from the <code>Component</code> superclass, and the Ember-specific items we are importing using <a href=\"/en-US/docs/Web/JavaScript/Guide/Modules\">JavaScript module syntax</a>) — the rest of the file is vanilla JavaScript, and would work in any application. The <code>@action</code> decorator declares that the function is an \"action\", meaning it's a type of function that will be invoked from an event that occurred in the template. <code>@action</code> also binds the <code>this</code> of the function to the class instance.</p>\n<div class=\"notecard note\">\n<p><strong>Note:</strong>\nA decorator is basically a wrapper function, which wraps and calls other functions or properties, providing additional functionality along the way. For example, the <code>@tracked</code> decorator (see slightly later on) runs code it is applied to, but additionally tracks it and automatically updates the app when values change. <a href=\"https://www.sitepoint.com/javascript-decorators-what-they-are/\" class=\"external\" target=\"_blank\">Read JavaScript Decorators: What They Are and When to Use Them</a> for more general information on decorators.</p>\n</div>\n<p>Coming back to our browser tab with the app running, we can type whatever we want, and when we hit <kbd>Enter</kbd> we'll be greeted with an alert message telling us exactly what we typed.</p>\n<p><img src=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/Ember_interactivity_events_state/todos-hello-there-alert.png\" alt=\"the initial placeholder state of the add function, showing the text entered into the input elements being alerted back to you.\" width=\"739\" height=\"676\" loading=\"lazy\"></p>\n<p>With the interactivity of the header input out of the way, we need a place to store todos so that other components can access them.</p>"}},{"type":"prose","value":{"id":"storing_todos_with_a_service","title":"Storing Todos with a service","isH3":false,"content":"<p>Ember has built-in application-level <strong>state</strong> management that we can use to manage the storage of our todos and allow each of our components to access data from that application-level state. Ember calls these constructs <a href=\"https://guides.emberjs.com/release/services/\" class=\"external\" target=\"_blank\">Services</a>, and they live for the entire lifetime of the page (a page refresh will clear them; persisting the data for longer is beyond the scope of this tutorial).</p>\n<p>Run this terminal command to generate a service for us to store our todo-list data in:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">bash</span></div><pre class=\"brush: bash notranslate\"><code>ember generate service todo-data\n</code></pre></div>\n<p>This should give you a terminal output like so:</p>\n<pre class=\"brush: plain notranslate\">installing service\n create app/services/todo-data.js\ninstalling service-test\n create tests/unit/services/todo-data-test.js\n</pre>\n<p>This creates a <code>todo-data.js</code> file inside the <code>todomvc/app/services</code> directory to contain our service, which initially contains an import statement and an empty class:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>import Service from \"@ember/service\";\n\nexport default class TodoDataService extends Service {}\n</code></pre></div>\n<p>First of all, we want to define <em>what a todo is</em>. We know that we want to track both the text of a todo, and whether or not it is completed.</p>\n<p>Add the following <code>import</code> statement below the existing one:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>import { tracked } from \"@glimmer/tracking\";\n</code></pre></div>\n<p>Now add the following class below the previous line you added:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>class Todo {\n @tracked text = \"\";\n @tracked isCompleted = false;\n\n constructor(text) {\n this.text = text;\n }\n}\n</code></pre></div>\n<p>This class represents a todo — it contains a <code>@tracked text</code> property containing the text of the todo, and a <code>@tracked isCompleted</code> property that specifies whether the todo has been completed or not. When instantiated, a <code>Todo</code> object will have an initial <code>text</code> value equal to the text given to it when created (see below), and an <code>isCompleted</code> value of <code>false</code>. The only Ember-specific part of this class is the <code>@tracked</code> decorator — this hooks in to the reactivity system and allows Ember to update what you're seeing in your app automatically if the tracked properties change. <a href=\"https://api.emberjs.com/ember/3.15/functions/@glimmer%2Ftracking/tracked\" class=\"external\" target=\"_blank\">More information on tracked can be found here</a>.</p>\n<p>Now it's time to add to the body of the service.</p>\n<p>First add another <code>import</code> statement below the previous one, to make actions available inside the service:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>import { action } from \"@ember/object\";\n</code></pre></div>\n<p>Update the existing <code>export default class TodoDataService extends Service { }</code> block as follows:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>export default class TodoDataService extends Service {\n @tracked todos = [];\n\n @action\n add(text) {\n let newTodo = new Todo(text);\n\n this.todos = [...this.todos, newTodo];\n }\n}\n</code></pre></div>\n<p>Here, the <code>todos</code> property on the service will maintain our list of todos contained inside an array, and we'll mark it with <code>@tracked</code>, because when the value of <code>todos</code> is updated we want the UI to update as well.</p>\n<p>And just like before, the <code>add()</code> function that will be called from the template gets annotated with the <code>@action</code> decorator to bind it to the class instance. We <a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax\">spread our <code>todos</code> array</a> to add <code>newTodo</code> to it, which creates a new array and will trigger the reactivity system to update the UI.</p>"}},{"type":"prose","value":{"id":"using_the_service_from_our_header_component","title":"Using the service from our header component","isH3":false,"content":"<p>Now that we've defined a way to add todos, we can interact with this service from the <code>header.js</code> input component to actually start adding them.</p>\n<p>First of all, the service needs to be injected into the template via the <code>@inject</code> decorator, which we'll rename to <code>@service</code> for semantic clarity. To do this, add the following <code>import</code> line to <code>header.js</code>, beneath the two existing <code>import</code> lines:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>import { inject as service } from \"@ember/service\";\n</code></pre></div>\n<p>With this import in place, we can now make the <code>todo-data</code> service available inside the <code>HeaderComponent</code> class via the <code>todos</code> object, using the <code>@service</code> decorator. Add the following line just below the opening <code>export…</code> line:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>@service('todo-data') todos;\n</code></pre></div>\n<p>Now the placeholder <code>alert(text);</code> line can be replaced with a call to our new <code>add()</code> function. Replace it with the following:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>this.todos.add(text);\n</code></pre></div>\n<p>If we try this out in the todo app in our browser (<code>npm start</code>, go to <code>localhost:4200</code>), it will look like nothing happens after hitting the <kbd>Enter</kbd> key (although the fact that the app builds without any errors is a good sign). Using the <a href=\"https://guides.emberjs.com/release/ember-inspector/installation/\" class=\"external\" target=\"_blank\">Ember Inspector</a> however, we can see that our todo was added:</p>\n<p><img src=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/Ember_interactivity_events_state/todos-in-ember-inspector.gif\" alt=\"The app being shown in the Ember inspector, to prove that added todos are being stored by the service, even if they are not being displayed in the UI yet\" width=\"736\" height=\"606\" loading=\"lazy\"></p>"}},{"type":"prose","value":{"id":"displaying_our_todos","title":"Displaying our todos","isH3":false,"content":"<p>Now that we know that we can create todos, there needs to be a way to swap out our static \"Buy Movie Tickets\" todos with the todos we're actually creating. In the <code>TodoList</code> component, we'll want to get the todos out of the service, and render a <code>Todo</code> component for each todo.</p>\n<p>In order to retrieve the todos from the service, our <code>TodoList</code> component first needs a backing component class to contain this functionality. Press <kbd>Ctrl</kbd> + <kbd>C</kbd> to stop the development server, and enter the following terminal command:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">bash</span></div><pre class=\"brush: bash notranslate\"><code>ember generate component-class todo-list\n</code></pre></div>\n<p>This generates the new component class <code>todomvc/app/components/todo-list.js</code>.</p>\n<p>Populate this file with the following code, which exposes the <code>todo-data</code> service, via the <code>todos</code> property, to our template. This makes it accessible via <code>this.todos</code> inside both the class and the template:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>import Component from \"@glimmer/component\";\nimport { inject as service } from \"@ember/service\";\n\nexport default class TodoListComponent extends Component {\n @service(\"todo-data\") todos;\n}\n</code></pre></div>\n<p>One issue here is that our service is called <code>todos</code>, but the list of todos is also called <code>todos</code>, so currently we would access the data using <code>this.todos.todos</code>. This is not intuitive, so we'll add a <a href=\"/en-US/docs/Web/JavaScript/Reference/Functions/get\">getter</a> to the <code>todos</code> service called <code>all</code>, which will represent all todos.</p>\n<p>To do this, go back to your <code>todo-data.js</code> file and add the following below the <code>@tracked todos = [];</code> line:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>get all() {\n return this.todos;\n}\n</code></pre></div>\n<p>Now we can access the data using <code>this.todos.all</code>, which is much more intuitive. To put this in action, go to your <code>todo-list.hbs</code> component, and replace the static component calls:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">hbs</span></div><pre class=\"brush: hbs notranslate\"><code><Todo />\n<Todo />\n</code></pre></div>\n<p>With a dynamic <code>#each</code> block (which is basically syntactic sugar over the top of JavaScript's <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach\"><code>forEach()</code></a>) that creates a <code><Todo /></code> component for each todo available in the list of todos returned by the service's <code>all()</code> getter:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">hbs</span></div><pre class=\"brush: hbs notranslate\"><code>{{#each this.todos.all as |todo|}}\n<Todo @todo={{todo}} />\n{{/each}}\n</code></pre></div>\n<p>Another way to look at this:</p>\n<ul>\n<li><code>this</code> — the rendering context / component instance.</li>\n<li><code>todos</code> — a property on <code>this</code>, which we defined in the <code>todo-list.js</code> component using <code>@service('todo-data') todos;</code>. This is a reference to the <code>todo-data</code> service, allowing us to interact with the service instance directly.</li>\n<li><code>all</code> — a getter on the <code>todo-data</code> service that returns all the todos.</li>\n</ul>\n<p>Try starting the server again and navigating to our app, and you'll find that it works! Well, sort of. Whenever you enter a new Todo item, a new list item appears below the text input, but unfortunately it always says \"Buy Movie Tickets\".</p>\n<p>This is because the text label inside each list item is hardcoded to that text, as seen in <code>todo.hbs</code>:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">hbs</span></div><pre class=\"brush: hbs notranslate\"><code><label>Buy Movie Tickets</label>\n</code></pre></div>\n<p>Update this line to use the Argument <code>@todo</code> — which will represent the Todo that we passed in to this component when it was invoked in <code>todo-list.hbs</code>, in the line <code><Todo @todo={{todo}} /></code>:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">hbs</span></div><pre class=\"brush: hbs notranslate\"><code><label>{{@todo.text}}</label>\n</code></pre></div>\n<p>OK, try it again. You should find that now the text submitted in the <code><input></code> is properly reflected in the UI:</p>\n<p><img src=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/Ember_interactivity_events_state/todos-being-appended-with-correct-text.gif\" alt=\"The app being shown in its final state of this article, with entered todo items being shown in the UI\" width=\"849\" height=\"662\" loading=\"lazy\"></p>"}},{"type":"prose","value":{"id":"summary","title":"Summary","isH3":false,"content":"<p>OK, so that's great progress for now. We can now add todo items to our app, and the state of the data is tracked using our service. Next we'll move on to getting our footer functionality working, including the todo counter, and look at conditional rendering, including correctly styling todos when they've been checked. We'll also wire up our \"Clear completed\" button.</p>\n<ul class=\"prev-next\"><li><a class=\"button secondary\" href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/Ember_structure_componentization\"><span class=\"button-wrap\"> Previous </span></a></li><li><a class=\"button secondary\" href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries\"><span class=\"button-wrap\"> Overview: JavaScript frameworks and libraries</span></a></li><li><a class=\"button secondary\" href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/Ember_conditional_footer\"><span class=\"button-wrap\"> Next </span></a></li></ul>"}}],"isActive":true,"isMarkdown":true,"isTranslated":false,"locale":"en-US","mdn_url":"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/Ember_interactivity_events_state","modified":"2024-12-19T15:37:45.000Z","native":"English (US)","noIndexing":false,"other_translations":[{"locale":"de","title":"Ember-Interaktivität: Ereignisse, Klassen und Zustand","native":"Deutsch"}],"pageTitle":"Ember interactivity: Events, classes and state - Learn web development | MDN","parents":[{"uri":"/en-US/docs/Learn_web_development","title":"Learn"},{"uri":"/en-US/docs/Learn_web_development/Core","title":"Core learning modules"},{"uri":"/en-US/docs/Learn_web_development/Core/Frameworks_libraries","title":"JavaScript frameworks and libraries"},{"uri":"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/Ember_interactivity_events_state","title":"Ember interactivity: Events, classes and state"}],"popularity":null,"short_title":"Ember interactivity: Events, classes and state","sidebarHTML":"<ol><li class=\"section\"><a href=\"/en-US/docs/Learn_web_development/Getting_started\">Getting started modules</a></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Getting_started/Environment_setup\">Environment setup</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Environment_setup/Installing_software\">Installing basic software</a></li><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Environment_setup/Browsing_the_web\">Browsing the web</a></li><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Environment_setup/Code_editors\">Code editors</a></li><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Environment_setup/Dealing_with_files\">Dealing with files</a></li><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Environment_setup/Command_line\">Command line crash course</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Getting_started/Your_first_website\">Your first website</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Your_first_website/What_will_your_website_look_like\">What will your website look like?</a></li><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Your_first_website/Creating_the_content\">HTML: Creating the content</a></li><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Your_first_website/Styling_the_content\">CSS: Styling the content</a></li><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Your_first_website/Adding_interactivity\">JavaScript: Adding interactivity</a></li><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Your_first_website/Publishing_your_website\">Publishing your website</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Getting_started/Web_standards\">Web standards</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Web_standards/How_the_web_works\">How the web works</a></li><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Web_standards/The_web_standards_model\">The web standards model</a></li><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Web_standards/How_browsers_load_websites\">How browsers load websites</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Getting_started/Soft_skills\">Soft skills</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Soft_skills/Research_and_learning\">Research and learning</a></li><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Soft_skills/Collaboration_and_teamwork\">Collaboration and teamwork</a></li><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Soft_skills/Workflows_and_processes\">Workflows and processes</a></li><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Soft_skills/Job_interviews\">Succeeding in job interviews</a></li></ol></details></li><li class=\"section\"><a href=\"/en-US/docs/Learn_web_development/Core\">Core modules</a></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content\">Structuring content with HTML</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content/Basic_HTML_syntax\">Basic HTML syntax</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content/Webpage_metadata\">What's in the head? Webpage metadata</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content/Headings_and_paragraphs\">Headings and paragraphs in HTML</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content/Emphasis_and_importance\">Emphasis and importance</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content/Lists\">Lists</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content/Structuring_documents\">Structuring documents</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content/Advanced_text_features\">Advanced text features</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content/Creating_links\">Creating links</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content/Marking_up_a_letter\">Challenge: Marking up a letter</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content/Structuring_a_page_of_content\">Challenge: Structuring a page of content</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content/HTML_images\">HTML images</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content/HTML_video_and_audio\">HTML video and audio</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content/Mozilla_splash_page\">Challenge: Mozilla splash page</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content/HTML_table_basics\">HTML table basics</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content/Table_accessibility\">HTML table accessibility</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content/Planet_data_table\">Challenge: Structuring a planet data table</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content/HTML_forms\">Forms and buttons in HTML</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content/Debugging_HTML\">Debugging HTML</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics\">CSS styling basics</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics/What_is_CSS\">What is CSS?</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics/Getting_started\">Getting started with CSS</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics/Styling_a_bio_page\">Challenge: Styling a biography page</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics/Basic_selectors\">Basic CSS selectors</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics/Attribute_selectors\">Attribute selectors</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics/Pseudo_classes_and_elements\">Pseudo-classes and pseudo-elements</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics/Combinators\">Combinators</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics/Box_model\">The box model</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics/Handling_conflicts\">Handling conflicts</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics/Values_and_units\">CSS values and units</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics/Sizing\">Sizing items in CSS</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics/Backgrounds_and_borders\">Backgrounds and borders</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics/Overflow\">Overflowing content</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics/Images_media_forms\">Images, media, and form elements</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics/Tables\">Styling tables</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics/Debugging_CSS\">Debugging CSS</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics/Fundamental_CSS_comprehension\">Challenge: Fundamental CSS comprehension</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics/Fancy_letterheaded_paper\">Challenge: Creating fancy letterheaded paper</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Styling_basics/Cool-looking_box\">Challenge: A cool-looking box</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Core/Text_styling\">CSS text styling</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Core/Text_styling/Fundamentals\">Fundamental text and font styling</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Text_styling/Styling_lists\">Styling lists</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Text_styling/Styling_links\">Styling links</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Text_styling/Web_fonts\">Web fonts</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Text_styling/Typesetting_a_homepage\">Challenge: Typesetting a community school homepage</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Core/CSS_layout\">CSS layout</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Core/CSS_layout/Introduction\">Introduction to CSS layout</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/CSS_layout/Floats\">Floats</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/CSS_layout/Positioning\">Positioning</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/CSS_layout/Flexbox\">Flexbox</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/CSS_layout/Grids\">CSS grid layout</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/CSS_layout/Responsive_Design\">Responsive design</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/CSS_layout/Media_queries\">Media query fundamentals</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/CSS_layout/Fundamental_Layout_Comprehension\">Challenge: Fundamental layout comprehension</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Core/Scripting\">Dynamic scripting with JavaScript</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/What_is_JavaScript\">What is JavaScript?</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/A_first_splash\">A first splash into JavaScript</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/What_went_wrong\">What went wrong? Troubleshooting JavaScript</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/Variables\">Storing the information you need — Variables</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/Math\">Basic math in JavaScript — numbers and operators</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/Strings\">Handling text — strings in JavaScript</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/Useful_string_methods\">Useful string methods</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/Arrays\">Arrays</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/Silly_story_generator\">Challenge: Silly story generator</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/Conditionals\">Making decisions in your code — conditionals</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/Loops\">Looping code</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/Functions\">Functions — reusable blocks of code</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/Build_your_own_function\">Build your own function</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/Return_values\">Function return values</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/Events\">Introduction to events</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/Event_bubbling\">Event bubbling</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/Image_gallery\">Challenge: Image gallery</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/Object_basics\">JavaScript object basics</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/DOM_scripting\">DOM scripting introduction</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/Network_requests\">Making network requests with JavaScript</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/JSON\">Working with JSON</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Scripting/Debugging_JavaScript\">Debugging JavaScript and handling errors</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries\">JavaScript frameworks and libraries</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/Introduction\">Introduction to client-side frameworks</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/Main_features\">Framework main features</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/React_getting_started\">Getting started with React</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/React_todo_list_beginning\">Beginning our React todo list</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/React_components\">Componentizing our React app</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/React_interactivity_events_state\">React interactivity: Events and state</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/React_interactivity_filtering_conditional_rendering\">React interactivity: Editing, filtering, conditional rendering</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/React_accessibility\">Accessibility in React</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/React_resources\">React resources</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Core/Accessibility\">Accessibility</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Core/Accessibility/What_is_accessibility\">What is accessibility?</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Accessibility/Tooling\">Accessibility tooling and assistive technology</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Accessibility/HTML\">HTML: A good basis for accessibility</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Accessibility/CSS_and_JavaScript\">CSS and JavaScript accessibility best practices</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Accessibility/WAI-ARIA_basics\">WAI-ARIA basics</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Accessibility/Multimedia\">Accessible multimedia</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Accessibility/Mobile\">Mobile accessibility</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Accessibility/Accessibility_troubleshooting\">Challenge: Accessibility troubleshooting</a></li></ol></details></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Design_for_developers\">Design for developers</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Version_control\">Version control</a></li><li class=\"section\"><a href=\"/en-US/docs/Learn_web_development/Extensions\">Extension modules</a></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Extensions/Advanced_JavaScript_objects\">Advanced JavaScript objects</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Advanced_JavaScript_objects/Object_prototypes\">Object prototypes</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Advanced_JavaScript_objects/Object-oriented_programming\">Object-oriented programming</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Advanced_JavaScript_objects/Classes_in_JavaScript\">Classes in JavaScript</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Advanced_JavaScript_objects/Object_building_practice\">Object building practice</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Advanced_JavaScript_objects/Adding_bouncing_balls_features\">Challenge: Adding features to our bouncing balls demo</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Extensions/Client-side_APIs\">Client-side web APIs</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Client-side_APIs/Introduction\">Introduction to web APIs</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Client-side_APIs/Video_and_audio_APIs\">Video and Audio APIs</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Client-side_APIs/Drawing_graphics\">Drawing graphics</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Client-side_APIs/Client-side_storage\">Client-side storage</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Client-side_APIs/Third_party_APIs\">Third-party APIs</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Extensions/Async_JS\">Asynchronous JavaScript</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Async_JS/Introducing\">Introducing asynchronous JavaScript</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Async_JS/Promises\">How to use promises</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Async_JS/Implementing_a_promise-based_API\">How to implement a promise-based API</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Async_JS/Introducing_workers\">Introducing workers</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Async_JS/Sequencing_animations\">Challenge: Sequencing animations</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Extensions/Forms\">Web forms</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Forms/Your_first_form\">Your first form</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Forms/How_to_structure_a_web_form\">How to structure a web form</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Forms/Basic_native_form_controls\">Basic native form controls</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Forms/HTML5_input_types\">The HTML5 input types</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Forms/Other_form_controls\">Other form controls</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Forms/Styling_web_forms\">Styling web forms</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Forms/Advanced_form_styling\">Advanced form styling</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Forms/UI_pseudo-classes\">UI pseudo-classes</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Forms/Form_validation\">Client-side form validation</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Forms/Sending_and_retrieving_form_data\">Sending form data</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Extensions/Client-side_tools\">Understanding client-side tools</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Client-side_tools/Overview\">Client-side tooling overview</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Client-side_tools/Package_management\">Package management basics</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Client-side_tools/Introducing_complete_toolchain\">Introducing a complete toolchain</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Client-side_tools/Deployment\">Deploying our app</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side\">Server-side websites</a></summary><ol><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/First_steps\">Server-side first steps</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/First_steps/Introduction\">Introduction to the server side</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/First_steps/Client-Server_overview\">Client-Server Overview</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/First_steps/Web_frameworks\">Server-side web frameworks</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/First_steps/Website_security\">Website security</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Django\">Django web framework (Python)</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Django/Introduction\">Django introduction</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Django/development_environment\">Setting up a Django development environment</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Django/Tutorial_local_library_website\">Django Tutorial: The Local Library website</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Django/skeleton_website\">Django Tutorial Part 2: Creating a skeleton website</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Django/Models\">Django Tutorial Part 3: Using models</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Django/Admin_site\">Django Tutorial Part 4: Django admin site</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Django/Home_page\">Django Tutorial Part 5: Creating our home page</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Django/Generic_views\">Django Tutorial Part 6: Generic list and detail views</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Django/Sessions\">Django Tutorial Part 7: Sessions framework</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Django/Authentication\">Django Tutorial Part 8: User authentication and permissions</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Django/Forms\">Django Tutorial Part 9: Working with forms</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Django/Testing\">Django Tutorial Part 10: Testing a Django web application</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Django/Deployment\">Django Tutorial Part 11: Deploying Django to production</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Django/web_application_security\">Django web application security</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Django/django_assessment_blog\">Assessment: DIY Django mini blog</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs\">Express web framework (Node.js)</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/Introduction\">Express/Node introduction</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/development_environment\">Setting up a Node development environment</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/Tutorial_local_library_website\">Express Tutorial: The Local Library website</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/skeleton_website\">Express Tutorial Part 2: Creating a skeleton website</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/mongoose\">Express Tutorial Part 3: Using a Database (with Mongoose)</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/routes\">Express Tutorial Part 4: Routes and controllers</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/Displaying_data\">Express Tutorial Part 5: Displaying library data</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/forms\">Express Tutorial Part 6: Working with forms</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/deployment\">Express Tutorial Part 7: Deploying to production</a></li></ol></details></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Extensions/Performance\">Web performance</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Performance/why_web_performance\">The \"why\" of web performance</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Performance/What_is_web_performance\">What is web performance?</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Performance/Perceived_performance\">Perceived performance</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Performance/Measuring_performance\">Measuring performance</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Performance/Multimedia\">Multimedia: Images</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Performance/video\">Multimedia: video</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Performance/JavaScript\">JavaScript performance optimization</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Performance/HTML\">HTML performance optimization</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Performance/CSS\">CSS performance optimization</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Performance/business_case_for_performance\">The business case for web performance</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Extensions/Testing\">Testing</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Testing/Introduction\">Introduction to cross-browser testing</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Testing/Testing_strategies\">Strategies for carrying out testing</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Testing/HTML_and_CSS\">Handling common HTML and CSS problems</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Testing/Feature_detection\">Implementing feature detection</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Testing/Automated_testing\">Introduction to automated testing</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Testing/Your_own_automation_environment\">Setting up your own test automation environment</a></li></ol></details></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Transform_animate\">Transform and animate CSS</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Security_privacy\">Security and privacy</a></li><li class=\"section\">Further resources</li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Howto\">How to solve common problems</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Howto/Solve_HTML_problems\">Solve common HTML problems</a></li><li><a href=\"/en-US/docs/Learn_web_development/Howto/Solve_CSS_problems\">Solve common CSS problems</a></li><li><a href=\"/en-US/docs/Learn_web_development/Howto/Solve_JavaScript_problems\">Solve common JavaScript problems</a></li><li><a href=\"/en-US/docs/Learn_web_development/Howto/Web_mechanics\">Web mechanics</a></li><li><a href=\"/en-US/docs/Learn_web_development/Howto/Tools_and_setup\">Tools and setup</a></li><li><a href=\"/en-US/docs/Learn_web_development/Howto/Design_and_accessibility\">Design and accessibility</a></li></ol></details></li><li><a href=\"/en-US/docs/Learn_web_development/About\">About</a></li><li><a href=\"/en-US/docs/Learn_web_development/Educators\">Resources for educators</a></li><li><a href=\"/en-US/docs/Learn_web_development/Changelog\">Changelog</a></li></ol>","source":{"folder":"en-us/learn_web_development/core/frameworks_libraries/ember_interactivity_events_state","github_url":"https://github.com/mdn/content/blob/main/files/en-us/learn_web_development/core/frameworks_libraries/ember_interactivity_events_state/index.md","last_commit_url":"https://github.com/mdn/content/commit/5b20f5f4265f988f80f513db0e4b35c7e0cd70dc","filename":"index.md"},"summary":"At this point we'll start adding some interactivity to our app, providing the ability to add and display new todo items. Along the way, we'll look at using events in Ember, creating component classes to contain JavaScript code to control interactive features, and setting up a service to keep track of the data state of our app.","title":"Ember interactivity: Events, classes and state","toc":[{"text":"Adding Interactivity","id":"adding_interactivity"},{"text":"Creating todos","id":"creating_todos"},{"text":"Storing Todos with a service","id":"storing_todos_with_a_service"},{"text":"Using the service from our header component","id":"using_the_service_from_our_header_component"},{"text":"Displaying our todos","id":"displaying_our_todos"},{"text":"Summary","id":"summary"}],"pageType":"learn-module-chapter"}}</script></body></html>