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Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Getting_started_with_the_web/Dealing_with_files?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Dealing with files</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Getting_started_with_the_web/HTML_basics?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">HTML basics</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Getting_started_with_the_web/CSS_basics?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">CSS basics</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Getting_started_with_the_web/JavaScript_basics?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">JavaScript basics</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Getting_started_with_the_web/Publishing_your_website?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Publishing your website</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Getting_started_with_the_web/How_the_Web_works?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">How the web works</a></li> </ol> </details></li> <li class="section"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">HTML — Structuring the web</a></li> <li class="toggle"> <details> <summary>Introduction to HTML</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Introduction_to_HTML?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Introduction to HTML</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Introduction_to_HTML/Getting_started?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Getting started with HTML</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Introduction_to_HTML/The_head_metadata_in_HTML?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">What's in the head? Metadata in HTML</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Introduction_to_HTML/HTML_text_fundamentals?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">HTML text fundamentals</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Introduction_to_HTML/Creating_hyperlinks?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Creating hyperlinks</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Introduction_to_HTML/Advanced_text_formatting?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Advanced text formatting</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Introduction_to_HTML/Document_and_website_structure?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Document and website structure</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Introduction_to_HTML/Debugging_HTML?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Debugging HTML</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Introduction_to_HTML/Marking_up_a_letter?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Marking up a letter</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Introduction_to_HTML/Structuring_a_page_of_content?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Structuring a page of content</a></li> </ol> </details></li> <li class="toggle"> <details> <summary>Multimedia and embedding</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Multimedia_and_embedding?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Multimedia and embedding</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Multimedia_and_embedding/Images_in_HTML?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Images in HTML</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Multimedia_and_embedding/Video_and_audio_content?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Video and audio content</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Multimedia_and_embedding/Other_embedding_technologies?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">From object to iframe — other embedding technologies</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Multimedia_and_embedding/Adding_vector_graphics_to_the_Web?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Adding vector graphics to the web</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Multimedia_and_embedding/Responsive_images?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Responsive images</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Multimedia_and_embedding/Mozilla_splash_page?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Mozilla splash page</a></li> </ol> </details></li> <li class="toggle"> <details> <summary>HTML tables</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Tables?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">HTML tables</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Tables/Basics?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">HTML table basics</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Tables/Advanced?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">HTML table advanced features and accessibility</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Tables/Structuring_planet_data?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Structuring planet data</a></li> </ol> </details></li> <li class="section"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">CSS — Styling the web</a></li> <li class="toggle"> <details> <summary>CSS first steps</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/First_steps?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">CSS first steps</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/First_steps/What_is_CSS?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">What is CSS?</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/First_steps/Getting_started?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Getting started with CSS</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/First_steps/How_CSS_is_structured?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">How CSS is structured</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/First_steps/How_CSS_works?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">How CSS works</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/First_steps/Styling_a_biography_page?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Styling a biography page</a></li> </ol> </details></li> <li class="toggle"> <details> <summary>CSS building blocks</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">CSS building blocks</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/Selectors?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">CSS selectors</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/Selectors/Type_Class_and_ID_Selectors?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Type, class, and ID selectors</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/Selectors/Attribute_selectors?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Attribute selectors</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/Selectors/Pseudo-classes_and_pseudo-elements?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Pseudo-classes and pseudo-elements</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/Selectors/Combinators?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Combinators</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/Cascade_and_inheritance?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Cascade, specificity, and inheritance</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/Cascade_layers?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Cascade layers</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/The_box_model?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">The box model</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/Backgrounds_and_borders?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Backgrounds and borders</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/Handling_different_text_directions?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Handling different text directions</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/Overflowing_content?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Overflowing content</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/Values_and_units?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">CSS values and units</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/Sizing_items_in_CSS?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Sizing items in CSS</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/Images_media_form_elements?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Images, media, and form elements</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/Styling_tables?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Styling tables</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/Advanced_styling_effects?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Advanced styling effects</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/Debugging_CSS?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Debugging CSS</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/Organizing?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Organizing your CSS</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/Fundamental_CSS_comprehension?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Fundamental CSS comprehension</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/Creating_fancy_letterheaded_paper?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Creating fancy letterheaded paper</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/A_cool_looking_box?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">A cool-looking box</a></li> </ol> </details></li> <li class="toggle"> <details> <summary>Styling text</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Styling_text?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">CSS styling text</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Styling_text/Fundamentals?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Fundamental text and font styling</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Styling_text/Styling_lists?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Styling lists</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Styling_text/Styling_links?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Styling links</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Styling_text/Web_fonts?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Web fonts</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Styling_text/Typesetting_a_homepage?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Typesetting a community school homepage</a></li> </ol> </details></li> <li class="toggle"> <details> <summary>CSS layout</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/CSS_layout?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">CSS layout</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/CSS_layout/Introduction?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Introduction to CSS layout</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/CSS_layout/Normal_Flow?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Normal Flow</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/CSS_layout/Flexbox?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Flexbox</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/CSS_layout/Grids?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Grids</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/CSS_layout/Floats?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Floats</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/CSS_layout/Positioning?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Positioning</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/CSS_layout/Multiple-column_Layout?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Multiple-column layout</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/CSS_layout/Responsive_Design?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Responsive design</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/CSS_layout/Media_queries?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Beginner's guide to media queries</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/CSS_layout/Legacy_Layout_Methods?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Legacy layout methods</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/CSS_layout/Supporting_Older_Browsers?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Supporting older browsers</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/CSS_layout/Fundamental_Layout_Comprehension?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Fundamental layout comprehension</a></li> </ol> </details></li> <li class="section"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">JavaScript — Dynamic client-side scripting</a></li> <li class="toggle"> <details open> <summary>JavaScript first steps</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">JavaScript first steps</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/What_is_JavaScript?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">What is JavaScript?</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/A_first_splash?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">A first splash into JavaScript</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/What_went_wrong?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">What went wrong? Troubleshooting JavaScript</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Variables?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Storing the information you need — Variables</a></li> <li><em><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB" aria-current="page">Basic math in JavaScript — numbers and operators</a></em></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Strings?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Handling text — strings in JavaScript</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Useful_string_methods?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Useful string methods</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Arrays?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Arrays</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Silly_story_generator?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Silly story generator</a></li> </ol> </details></li> <li class="toggle"> <details> <summary>JavaScript building blocks</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Building_blocks?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">JavaScript building blocks</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Building_blocks/conditionals?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Making decisions in your code — conditionals</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Looping code</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Building_blocks/Functions?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Functions — reusable blocks of code</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Building_blocks/Build_your_own_function?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Build your own function</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Building_blocks/Return_values?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Function return values</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Building_blocks/Events?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Introduction to events</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Building_blocks/Event_bubbling?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Event bubbling</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Building_blocks/Image_gallery?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Image gallery</a></li> </ol> </details></li> <li class="toggle"> <details> <summary>Introducing JavaScript objects</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Objects?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Introducing JavaScript objects</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Objects/Basics?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">JavaScript object basics</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Objects/Object_prototypes?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Object prototypes</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Objects/Object-oriented_programming?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Object-oriented programming</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Objects/Classes_in_JavaScript?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Classes in JavaScript</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Objects/JSON?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Working with JSON</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Objects/Object_building_practice?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Object building practice</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Objects/Adding_bouncing_balls_features?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Adding features to our bouncing balls demo</a></li> </ol> </details></li> <li class="toggle"> <details> <summary>Asynchronous JavaScript</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Asynchronous?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Asynchronous JavaScript</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Asynchronous/Introducing?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Introducing asynchronous JavaScript</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Asynchronous/Promises?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">How to use promises</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Asynchronous/Implementing_a_promise-based_API?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">How to implement a promise-based API</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Asynchronous/Introducing_workers?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Introducing workers</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Asynchronous/Sequencing_animations?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Sequencing animations</a></li> </ol> </details></li> <li class="toggle"> <details> <summary>Client-side web APIs</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Client-side_web_APIs?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Client-side web APIs</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Introduction?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Introduction to web APIs</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Manipulating_documents?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Manipulating documents</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Fetching_data?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Fetching data from the server</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Third_party_APIs?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Third-party APIs</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Drawing_graphics?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Drawing graphics</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Video_and_audio_APIs?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Video and Audio APIs</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Client-side_storage?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Client-side storage</a></li> </ol> </details></li> <li class="section"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Forms?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Web forms — Working with user data</a></li> <li class="toggle"> <details> <summary>Web form building blocks</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Forms?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Web form building blocks</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Forms/Your_first_form?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Your first form</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Forms/How_to_structure_a_web_form?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">How to structure a web form</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Forms/Basic_native_form_controls?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Basic native form controls</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Forms/HTML5_input_types?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">The HTML5 input types</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Forms/Other_form_controls?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Other form controls</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Forms/Styling_web_forms?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Styling web forms</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Forms/Advanced_form_styling?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Advanced form styling</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Forms/UI_pseudo-classes?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">UI pseudo-classes</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Forms/Form_validation?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Client-side form validation</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Forms/Sending_and_retrieving_form_data?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Sending form data</a></li> </ol> </details></li> <li class="toggle"> <details> <summary>Advanced web form techniques</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Forms/How_to_build_custom_form_controls?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">How to build custom form controls</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Forms/Sending_forms_through_JavaScript?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Sending forms through JavaScript</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Forms/Property_compatibility_table_for_form_controls?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">CSS property compatibility table for form controls</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Forms/HTML_forms_in_legacy_browsers?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">HTML forms in legacy browsers</a></li> </ol> </details></li> <li class="section"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Accessibility?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Accessibility — Make the web usable by everyone</a></li> <li class="toggle"> <details> <summary>Accessibility guides</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Accessibility?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Accessibility</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Accessibility/What_is_accessibility?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">What is accessibility?</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Accessibility/HTML?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">HTML: A good basis for accessibility</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Accessibility/CSS_and_JavaScript?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">CSS and JavaScript accessibility best practices</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Accessibility/WAI-ARIA_basics?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">WAI-ARIA basics</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Accessibility/Multimedia?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Accessible multimedia</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Accessibility/Mobile?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Mobile accessibility</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Accessibility/Accessibility_troubleshooting?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Assessment: Accessibility troubleshooting</a></li> </ol> </details></li> <li class="section"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Performance?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Performance — Making websites fast and responsive</a></li> <li class="toggle"> <details> <summary>Performance guides</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Performance?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Web performance</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Performance/why_web_performance?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">The "why" of web performance</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Performance/What_is_web_performance?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">What is web performance?</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Performance/Perceived_performance?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Perceived performance</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Performance/Measuring_performance?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Measuring performance</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Performance/Multimedia?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Multimedia: Images</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Performance/video?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Multimedia: video</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Performance/JavaScript?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">JavaScript performance optimization</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Performance/HTML?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">HTML performance optimization</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Performance/CSS?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">CSS performance optimization</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Performance/business_case_for_performance?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">The business case for web performance</a></li> </ol> </details></li> <li class="section"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/MathML?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">MathML — Writing mathematics with MathML</a></li> <li class="toggle"> <details> <summary>MathML first steps</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/MathML/First_steps?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">MathML first steps</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/MathML/First_steps/Getting_started?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Getting started with MathML</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/MathML/First_steps/Text_containers?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">MathML Text Containers</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/MathML/First_steps/Fractions_and_roots?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">MathML fractions and roots</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/MathML/First_steps/Scripts?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">MathML scripted elements</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/MathML/First_steps/Tables?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">MathML tables</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/MathML/First_steps/Three_famous_mathematical_formulas?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Three famous mathematical formulas</a></li> </ol> </details></li> <li class="section"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Games?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Games — Developing games for the web</a></li> <li class="toggle"> <details> <summary>Guides and tutorials</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Games/Introduction?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Introduction to game development for the Web</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Games/Techniques?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Techniques for game development</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Games/Tutorials?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Tutorials</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Games/Publishing_games?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Publishing games</a></li> </ol> </details></li> <li class="section"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Tools and testing</a></li> <li class="toggle"> <details> <summary>Client-side web development tools</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Understanding client-side web development tools</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Overview?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Client-side tooling overview</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Command_line?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Command line crash course</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Package_management?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Package management basics</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Introducing_complete_toolchain?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Introducing a complete toolchain</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Deployment?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Deploying our app</a></li> </ol> </details></li> <li class="toggle"> <details> <summary>Introduction to client-side frameworks</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Introduction?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Introduction to client-side frameworks</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Main_features?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Framework main features</a></li> </ol> </details></li> <li class="toggle"> <details> <summary>React</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_getting_started?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Getting started with React</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_todo_list_beginning?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Beginning our React todo list</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_components?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Componentizing our React app</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_interactivity_events_state?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">React interactivity: Events and state</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_interactivity_filtering_conditional_rendering?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">React interactivity: Editing, filtering, conditional rendering</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_accessibility?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Accessibility in React</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_resources?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">React resources</a></li> </ol> </details></li> <li class="toggle"> <details> <summary>Ember</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_getting_started?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Getting started with Ember</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_structure_componentization?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Ember app structure and componentization</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_interactivity_events_state?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Ember interactivity: Events, classes and state</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_conditional_footer?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Ember Interactivity: Footer functionality, conditional rendering</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_routing?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Routing in Ember</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_resources?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Ember resources and troubleshooting</a></li> </ol> </details></li> <li class="toggle"> <details> <summary>Vue</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_getting_started?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Getting started with Vue</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_first_component?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Creating our first Vue component</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_rendering_lists?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Rendering a list of Vue components</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_methods_events_models?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Adding a new todo form: Vue events, methods, and models</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_styling?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Styling Vue components with CSS</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_computed_properties?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Using Vue computed properties</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_conditional_rendering?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Vue conditional rendering: editing existing todos</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_refs_focus_management?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Vue refs and lifecycle methods for focus management</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_resources?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Vue resources</a></li> </ol> </details></li> <li class="toggle"> <details> <summary>Svelte</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_getting_started?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Getting started with Svelte</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_Todo_list_beginning?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Starting our Svelte to-do list app</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_variables_props?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Dynamic behavior in Svelte: working with variables and props</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_components?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Componentizing our Svelte app</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_reactivity_lifecycle_accessibility?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Advanced Svelte: Reactivity, lifecycle, accessibility</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_stores?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Working with Svelte stores</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_TypeScript?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">TypeScript support in Svelte</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_deployment_next?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Deployment and next steps</a></li> </ol> </details></li> <li class="toggle"> <details> <summary>Angular</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_getting_started?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Getting started with Angular</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_todo_list_beginning?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Beginning our Angular todo list app</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_styling?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Styling our Angular app</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_item_component?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Creating an item component</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_filtering?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Filtering our to-do items</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_building?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Building Angular applications and further resources</a></li> </ol> </details></li> <li class="toggle"> <details> <summary>Git and GitHub</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/GitHub?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Git and GitHub</a></li> </ol> </details></li> <li class="toggle"> <details> <summary>Cross browser testing</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Cross browser testing</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Introduction?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Introduction to cross-browser testing</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Testing_strategies?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Strategies for carrying out testing</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/HTML_and_CSS?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Handling common HTML and CSS problems</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/JavaScript?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Handling common JavaScript problems</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Accessibility?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Handling common accessibility problems</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Feature_detection?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Implementing feature detection</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Automated_testing?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Introduction to automated testing</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Your_own_automation_environment?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Setting up your own test automation environment</a></li> </ol> </details></li> <li class="section"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Server-side website programming</a></li> <li class="toggle"> <details> <summary>First steps</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/First_steps?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Server-side website programming first steps</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/First_steps/Introduction?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Introduction to the server side</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/First_steps/Client-Server_overview?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Client-Server Overview</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/First_steps/Web_frameworks?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Server-side web frameworks</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/First_steps/Website_security?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Website security</a></li> </ol> </details></li> <li class="toggle"> <details> <summary>Django web framework (Python)</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Django?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Django Web Framework (Python)</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Django/Introduction?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Django introduction</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Django/development_environment?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Setting up a Django development environment</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Django/Tutorial_local_library_website?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Django Tutorial: The Local Library website</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Django/skeleton_website?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Django Tutorial Part 2: Creating a skeleton website</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Django/Models?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Django Tutorial Part 3: Using models</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Django/Admin_site?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Django Tutorial Part 4: Django admin site</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Django/Home_page?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Django Tutorial Part 5: Creating our home page</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Django/Generic_views?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Django Tutorial Part 6: Generic list and detail views</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Django/Sessions?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Django Tutorial Part 7: Sessions framework</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Django/Authentication?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Django Tutorial Part 8: User authentication and permissions</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Django/Forms?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Django Tutorial Part 9: Working with forms</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Django/Testing?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Django Tutorial Part 10: Testing a Django web application</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Django/Deployment?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Django Tutorial Part 11: Deploying Django to production</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Django/web_application_security?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Django web application security</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Django/django_assessment_blog?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Assessment: DIY Django mini blog</a></li> </ol> </details></li> <li class="toggle"> <details> <summary>Express Web Framework (Node.js/JavaScript)</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Express_Nodejs?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Express web framework (Node.js/JavaScript)</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Express_Nodejs/Introduction?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Express/Node introduction</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Express_Nodejs/development_environment?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Setting up a Node development environment</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Express_Nodejs/Tutorial_local_library_website?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Express Tutorial: The Local Library website</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Express_Nodejs/skeleton_website?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Express Tutorial Part 2: Creating a skeleton website</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Express_Nodejs/mongoose?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Express Tutorial Part 3: Using a Database (with Mongoose)</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Express_Nodejs/routes?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Express Tutorial Part 4: Routes and controllers</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Express_Nodejs/Displaying_data?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Express Tutorial Part 5: Displaying library data</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Express_Nodejs/forms?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Express Tutorial Part 6: Working with forms</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Server-side/Express_Nodejs/deployment?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Express Tutorial Part 7: Deploying to production</a></li> </ol> </details></li> <li class="section"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Common_questions?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Further resources</a></li> <li class="toggle"> <details> <summary>Common questions</summary> <ol> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Common_questions?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Common questions</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/HTML/Howto?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Use HTML to solve common problems</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Howto?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Use CSS to solve common problems</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/Howto?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Solve common problems in your JavaScript code</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Common_questions/Web_mechanics?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Web mechanics</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Common_questions/Tools_and_setup?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Tools and setup</a></li> <li><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Common_questions/Design_and_accessibility?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Design and accessibility</a></li> </ol> </details></li> </ol> </div> </div> <section class="place side"></section> </nav> </aside> <div class="toc-container"> <aside class="toc"> <nav> <div class="document-toc-container"> <section class="document-toc"> <header> <h2 class="document-toc-heading">In this article</h2> </header> <ul class="document-toc-list"> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#everybody_loves_math">Everybody loves math</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#arithmetic_operators">Arithmetic operators</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#increment_and_decrement_operators">Increment and decrement operators</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#assignment_operators">Assignment operators</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#active_learning_sizing_a_canvas_box">Active learning: sizing a canvas box</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#comparison_operators">Comparison operators</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#test_your_skills!">Test your skills!</a></li> <li class="document-toc-item "><a class="document-toc-link" href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#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>Basic math in JavaScript — numbers and operators</h1> </header> <div class="section-content"> <ul class="prev-next"> <li><a class="button secondary" href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Variables?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB"><span class="button-wrap"> Previous </span></a></li> <li><a class="button secondary" href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB"><span class="button-wrap"> Overview: JavaScript first steps</span></a></li> <li><a class="button secondary" href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Strings?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB"><span class="button-wrap"> Next </span></a></li> </ul> <p>At this point in the course, we discuss math in JavaScript — how we can use <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Glossary/Operator?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">operators</a> and other features to successfully manipulate numbers to do our bidding.</p> <figure class="table-container"> <table> <tbody> <tr> <th scope="row">Prerequisites:</th> <td>A basic understanding of HTML and CSS, an understanding of what JavaScript is.</td> </tr> <tr> <th scope="row">Objective:</th> <td>To gain familiarity with the basics of math in JavaScript.</td> </tr> </tbody> </table> </figure> </div> <section aria-labelledby="everybody_loves_math"> <h2 id="everybody_loves_math"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#everybody_loves_math">Everybody loves math</a></h2> <div class="section-content"> <p>Okay, maybe not. Some of us like math, some of us have hated math ever since we had to learn multiplication tables and long division in school, and some of us sit somewhere in between the two. But none of us can deny that math is a fundamental part of life that we can't get very far without. This is especially true when we are learning to program JavaScript (or any other language for that matter) — so much of what we do relies on processing numerical data, calculating new values, and so on, that you won't be surprised to learn that JavaScript has a full-featured set of math functions available.</p> <p>This article discusses only the basic parts that you need to know now.</p> </div> </section> <section aria-labelledby="types_of_numbers"> <h3 id="types_of_numbers"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#types_of_numbers">Types of numbers</a></h3> <div class="section-content"> <p>In programming, even the humble decimal number system that we all know so well is more complicated than you might think. We use different terms to describe different types of decimal numbers, for example:</p> <ul> <li><strong>Integers</strong> are numbers without a fractional part. They can either be positive or negative, e.g. 10, 400, or -5.</li> <li><strong>Floating point numbers</strong> (floats) have decimal points and decimal places, for example 12.5, and 56.7786543.</li> </ul> <p>We even have different types of number systems! Decimal is base 10 (meaning it uses 0–9 in each digit), but we also have things like:</p> <ul> <li><strong>Binary</strong> — The lowest level language of computers; 0s and 1s.</li> <li><strong>Octal</strong> — Base 8, uses 0–7 in each digit.</li> <li><strong>Hexadecimal</strong> — Base 16, uses 0–9 and then a–f in each digit. You may have encountered these numbers before when setting <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/CSS/Building_blocks/Values_and_units?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#hexadecimal_rgb_values">colors in CSS</a>.</li> </ul> <p><strong>Before you start to get worried about your brain melting, stop right there!</strong> For a start, we are just going to stick to decimal numbers throughout this course; you'll rarely come across a need to start thinking about other types, if ever.</p> <p>The second bit of good news is that unlike some other programming languages, JavaScript only has one data type for numbers, both integers and decimals — you guessed it, <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB"><code>Number</code></a>. This means that whatever type of numbers you are dealing with in JavaScript, you handle them in exactly the same way.</p> <div class="notecard note"> <p><strong>Note:</strong> Actually, JavaScript has a second number type, <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Glossary/BigInt?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">BigInt</a>, used for very, very large integers. But for the purposes of this course, we'll just worry about <code>Number</code> values.</p> </div> </div> </section> <section aria-labelledby="its_all_numbers_to_me"> <h3 id="its_all_numbers_to_me"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#its_all_numbers_to_me">It's all numbers to me</a></h3> <div class="section-content"> <p>Let's quickly play with some numbers to reacquaint ourselves with the basic syntax we need. Enter the commands listed below into your <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Common_questions/Tools_and_setup/What_are_browser_developer_tools?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">developer tools JavaScript console</a>.</p> <ol> <li><p>First of all, let's declare a couple of variables and initialize them with an integer and a float, respectively, then type the variable names back in to check that everything is in order:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>const myInt = 5; const myFloat = 6.667; myInt; myFloat; </code></pre> </div></li> <li><p>Number values are typed in without quote marks — try declaring and initializing a couple more variables containing numbers before you move on.</p></li> <li><p>Now let's check that both our original variables are of the same datatype. There is an operator called <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Operators/typeof?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB"><code>typeof</code></a> in JavaScript that does this. Enter the below two lines as shown:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>typeof myInt; typeof myFloat; </code></pre> </div><p>You should get <code>"number"</code> returned in both cases — this makes things a lot easier for us than if different numbers had different data types, and we had to deal with them in different ways. Phew!</p></li> </ol> </div> </section> <section aria-labelledby="useful_number_methods"> <h3 id="useful_number_methods"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#useful_number_methods">Useful Number methods</a></h3> <div class="section-content"> <p>The <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB"><code>Number</code></a> object, an instance of which represents all standard numbers you'll use in your JavaScript, has a number of useful methods available on it for you to manipulate numbers. We don't cover these in detail in this article because we wanted to keep it as an introduction and only cover the real basic essentials for now; however, once you've read through this module a couple of times it is worth going to the object reference pages and learning more about what's available.</p> <p>For example, to round your number to a fixed number of decimal places, use the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/toFixed?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB"><code>toFixed()</code></a> method. Type the following lines into your browser's <a href="https://translate.google.com/website?sl=pl&tl=fr&hl=en-GB&u=https://firefox-source-docs.mozilla.org/devtools-user/web_console/index.html" class="external" target="_blank">console</a>:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>const lotsOfDecimal = 1.766584958675746364; lotsOfDecimal; const twoDecimalPlaces = lotsOfDecimal.toFixed(2); twoDecimalPlaces; </code></pre> </div> </div> </section> <section aria-labelledby="converting_to_number_data_types"> <h3 id="converting_to_number_data_types"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#converting_to_number_data_types">Converting to number data types</a></h3> <div class="section-content"> <p>Sometimes you might end up with a number that is stored as a string type, which makes it difficult to perform calculations with it. This most commonly happens when data is entered into a <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Forms?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">form</a> input, and the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/HTML/Element/input/text?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">input type is text</a>. There is a way to solve this problem — passing the string value into the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/Number?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB"><code>Number()</code></a> constructor to return a number version of the same value.</p> <p>For example, try typing these lines into your console:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>let myNumber = "74"; myNumber += 3; </code></pre> </div> <p>You end up with the result 743, not 77, because <code>myNumber</code> is actually defined as a string. You can test this by typing in the following:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>typeof myNumber; </code></pre> </div> <p>To fix the calculation, you can do this:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>let myNumber = "74"; myNumber = Number(myNumber) + 3; </code></pre> </div> <p>The result is then 77, as initially expected.</p> </div> </section> <section aria-labelledby="arithmetic_operators"> <h2 id="arithmetic_operators"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#arithmetic_operators">Arithmetic operators</a></h2> <div class="section-content"> <p>Arithmetic operators are used for performing mathematical calculations in JavaScript:</p> <figure class="table-container"> <table class="standard-table"> <thead> <tr> <th scope="col">Operator</th> <th scope="col">Name</th> <th scope="col">Purpose</th> <th scope="col">Example</th> </tr> </thead> <tbody> <tr> <td><code>+</code></td> <td>Addition</td> <td>Adds two numbers together.</td> <td><code>6 + 9</code></td> </tr> <tr> <td><code>-</code></td> <td>Subtraction</td> <td>Subtracts the right number from the left.</td> <td><code>20 - 15</code></td> </tr> <tr> <td><code>*</code></td> <td>Multiplication</td> <td>Multiplies two numbers together.</td> <td><code>3 * 7</code></td> </tr> <tr> <td><code>/</code></td> <td>Division</td> <td>Divides the left number by the right.</td> <td><code>10 / 5</code></td> </tr> <tr> <td><code>%</code></td> <td>Remainder (sometimes called modulo)</td> <td><p>Returns the remainder left over after you've divided the left number into a number of integer portions equal to the right number.</p></td> <td><p><code>8 % 3</code> (returns 2, as three goes into 8 twice, leaving 2 left over).</p></td> </tr> <tr> <td><code>**</code></td> <td>Exponent</td> <td>Raises a <code>base</code> number to the <code>exponent</code> power, that is, the <code>base</code> number multiplied by itself, <code>exponent</code> times.</td> <td><code>5 ** 2</code> (returns <code>25</code>, which is the same as <code>5 * 5</code>).</td> </tr> </tbody> </table> </figure> <div class="notecard note"> <p><strong>Note:</strong> You'll sometimes see numbers involved in arithmetic referred to as <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Glossary/Operand?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">operands</a>.</p> </div> <div class="notecard note"> <p><strong>Note:</strong> You may sometimes see exponents expressed using the older <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/pow?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB"><code>Math.pow()</code></a> method, which works in a very similar way. For example, in <code>Math.pow(7, 3)</code>, <code>7</code> is the base and <code>3</code> is the exponent, so the result of the expression is <code>343</code>. <code>Math.pow(7, 3)</code> is equivalent to <code>7**3</code>.</p> </div> <p>We probably don't need to teach you how to do basic math, but we would like to test your understanding of the syntax involved. Try entering the examples below into your <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/Common_questions/Tools_and_setup/What_are_browser_developer_tools?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">developer tools JavaScript console</a> to familiarize yourself with the syntax.</p> <ol> <li><p>First try entering some simple examples of your own, such as</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>10 + 7; 9 * 8; 60 % 3; </code></pre> </div></li> <li><p>You can also try declaring and initializing some numbers inside variables, and try using those in the sums — the variables will behave exactly like the values they hold for the purposes of the sum. For example:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>const num1 = 10; const num2 = 50; 9 * num1; num1 ** 3; num2 / num1; </code></pre> </div></li> <li><p>Last for this section, try entering some more complex expressions, such as:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>5 + 10 * 3; (num2 % 9) * num1; num2 + num1 / 8 + 2; </code></pre> </div></li> </ol> <p>Parts of this last set of calculations might not give you quite the result you were expecting; the section below might well give the answer as to why.</p> </div> </section> <section aria-labelledby="operator_precedence"> <h3 id="operator_precedence"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#operator_precedence">Operator precedence</a></h3> <div class="section-content"> <p>Let's look at the last example from above, assuming that <code>num2</code> holds the value 50 and <code>num1</code> holds the value 10 (as originally stated above):</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>num2 + num1 / 8 + 2; </code></pre> </div> <p>As a human being, you may read this as <em>"50 plus 10 equals 60"</em>, then <em>"8 plus 2 equals 10"</em>, and finally <em>"60 divided by 10 equals 6"</em>.</p> <p>But the browser does <em>"10 divided by 8 equals 1.25"</em>, then <em>"50 plus 1.25 plus 2 equals 53.25"</em>.</p> <p>This is because of <strong>operator precedence</strong> — some operators are applied before others when calculating the result of a calculation (referred to as an <em>expression</em>, in programming). Operator precedence in JavaScript is the same as is taught in math classes in school — multiply and divide are always done first, then add and subtract (the calculation is always evaluated from left to right).</p> <p>If you want to override operator precedence, you can put parentheses around the parts that you want to be explicitly dealt with first. So to get a result of 6, we could do this:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>(num2 + num1) / (8 + 2); </code></pre> </div> <p>Try it and see.</p> <div class="notecard note"> <p><strong>Note:</strong> A full list of all JavaScript operators and their precedence can be found in <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Reference/Operators/Operator_precedence?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Operator precedence</a>.</p> </div> </div> </section> <section aria-labelledby="increment_and_decrement_operators"> <h2 id="increment_and_decrement_operators"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#increment_and_decrement_operators">Increment and decrement operators</a></h2> <div class="section-content"> <p>Sometimes you'll want to repeatedly add or subtract one to or from a numeric variable value. This can be conveniently done using the increment (<code>++</code>) and decrement (<code>--</code>) operators. We used <code>++</code> in our "Guess the number" game back in our <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/A_first_splash?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">first splash into JavaScript</a> article, when we added 1 to our <code>guessCount</code> variable to keep track of how many guesses the user has left after each turn.</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>guessCount++; </code></pre> </div> <p>Let's try playing with these in your console. For a start, note that you can't apply these directly to a number, which might seem strange, but we are assigning a variable a new updated value, not operating on the value itself. The following will return an error:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js example-bad notranslate"><code>3++; </code></pre> </div> <p>So, you can only increment an existing variable. Try this:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>let num1 = 4; num1++; </code></pre> </div> <p>Okay, strangeness number 2! When you do this, you'll see a value of 4 returned — this is because the browser returns the current value, <em>then</em> increments the variable. You can see that it's been incremented if you return the variable value again:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>num1; </code></pre> </div> <p>The same is true of <code>--</code> : try the following</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>let num2 = 6; num2--; num2; </code></pre> </div> <div class="notecard note"> <p><strong>Note:</strong> You can make the browser do it the other way round — increment/decrement the variable <em>then</em> return the value — by putting the operator at the start of the variable instead of the end. Try the above examples again, but this time use <code>++num1</code> and <code>--num2</code>.</p> </div> </div> </section> <section aria-labelledby="assignment_operators"> <h2 id="assignment_operators"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#assignment_operators">Assignment operators</a></h2> <div class="section-content"> <p>Assignment operators are operators that assign a value to a variable. We have already used the most basic one, <code>=</code>, loads of times — it assigns the variable on the left the value stated on the right:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>let x = 3; // x contains the value 3 let y = 4; // y contains the value 4 x = y; // x now contains the same value y contains, 4 </code></pre> </div> <p>But there are some more complex types, which provide useful shortcuts to keep your code neater and more efficient. The most common are listed below:</p> <figure class="table-container"> <table class="standard-table no-markdown"> <thead> <tr> <th scope="col">Operator</th> <th scope="col">Name</th> <th scope="col">Purpose</th> <th scope="col">Example</th> <th scope="col">Shortcut for</th> </tr> </thead> <tbody> <tr> <td><code>+=</code></td> <td>Addition assignment</td> <td>Adds the value on the right to the variable value on the left, then returns the new variable value</td> <td><code>x += 4;</code></td> <td><code>x = x + 4;</code></td> </tr> <tr> <td><code>-=</code></td> <td>Subtraction assignment</td> <td>Subtracts the value on the right from the variable value on the left, and returns the new variable value</td> <td><code>x -= 3;</code></td> <td><code>x = x - 3;</code></td> </tr> <tr> <td><code>*=</code></td> <td>Multiplication assignment</td> <td>Multiplies the variable value on the left by the value on the right, and returns the new variable value</td> <td><code>x *= 3;</code></td> <td><code>x = x * 3;</code></td> </tr> <tr> <td><code>/=</code></td> <td>Division assignment</td> <td>Divides the variable value on the left by the value on the right, and returns the new variable value</td> <td><code>x /= 5;</code></td> <td><code>x = x / 5;</code></td> </tr> </tbody> </table> </figure> <p>Try typing some of the above examples into your console, to get an idea of how they work. In each case, see if you can guess what the value is before you type in the second line.</p> <p>Note that you can quite happily use other variables on the right-hand side of each expression, for example:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>let x = 3; // x contains the value 3 let y = 4; // y contains the value 4 x *= y; // x now contains the value 12 </code></pre> </div> <div class="notecard note"> <p><strong>Note:</strong> There are lots of <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Guide/Expressions_and_operators?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#assignment_operators">other assignment operators available</a>, but these are the basic ones you should learn now.</p> </div> </div> </section> <section aria-labelledby="active_learning_sizing_a_canvas_box"> <h2 id="active_learning_sizing_a_canvas_box"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#active_learning_sizing_a_canvas_box">Active learning: sizing a canvas box</a></h2> <div class="section-content"> <p>In this exercise, you will manipulate some numbers and operators to change the size of a box. The box is drawn using a browser API called the <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/API/Canvas_API?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Canvas API</a>. There is no need to worry about how this works — just concentrate on the math for now. The width and height of the box (in pixels) are defined by the variables <code>x</code> and <code>y</code>, which are initially both given a value of 50.</p><iframe width="100%" height="620" src="https://mdn.github.io/learning-area/javascript/introduction-to-js-1/maths/editable_canvas.html" loading="lazy"></iframe> <p><strong><a href="https://translate.google.com/website?sl=pl&tl=fr&hl=en-GB&u=https://mdn.github.io/learning-area/javascript/introduction-to-js-1/maths/editable_canvas.html" class="external" target="_blank">Open in new window</a></strong></p> <p>In the editable code box above, there are two lines marked with a comment that we'd like you to update to make the box grow/shrink to certain sizes, using certain operators and/or values in each case. Let's try the following:</p> <ul> <li>Change the line that calculates x so the box is still 50px wide, but the 50 is calculated using the numbers 43 and 7 and an arithmetic operator.</li> <li>Change the line that calculates y so the box is 75px high, but the 75 is calculated using the numbers 25 and 3 and an arithmetic operator.</li> <li>Change the line that calculates x so the box is 250px wide, but the 250 is calculated using two numbers and the remainder (modulo) operator.</li> <li>Change the line that calculates y so the box is 150px high, but the 150 is calculated using three numbers and the subtraction and division operators.</li> <li>Change the line that calculates x so the box is 200px wide, but the 200 is calculated using the number 4 and an assignment operator.</li> <li>Change the line that calculates y so the box is 200px high, but the 200 is calculated using the numbers 50 and 3, the multiplication operator, and the addition assignment operator.</li> </ul> <p>Don't worry if you totally mess the code up. You can always press the Reset button to get things working again. After you've answered all the above questions correctly, feel free to play with the code some more or create your own challenges.</p> </div> </section> <section aria-labelledby="comparison_operators"> <h2 id="comparison_operators"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#comparison_operators">Comparison operators</a></h2> <div class="section-content"> <p>Sometimes we will want to run true/false tests, then act accordingly depending on the result of that test — to do this we use <strong>comparison operators</strong>.</p> <figure class="table-container"> <table> <thead> <tr> <th>Operator</th> <th>Name</th> <th>Purpose</th> <th>Example</th> </tr> </thead> <tbody> <tr> <td><code>===</code></td> <td>Strict equality</td> <td>Tests whether the left and right values are identical to one another</td> <td><code>5 === 2 + 4</code></td> </tr> <tr> <td><code>!==</code></td> <td>Strict-non-equality</td> <td>Tests whether the left and right values are <strong>not</strong> identical to one another</td> <td><code>5 !== 2 + 3</code></td> </tr> <tr> <td><code><</code></td> <td>Less than</td> <td>Tests whether the left value is smaller than the right one.</td> <td><code>10 < 6</code></td> </tr> <tr> <td><code>></code></td> <td>Greater than</td> <td>Tests whether the left value is greater than the right one.</td> <td><code>10 > 20</code></td> </tr> <tr> <td><code><=</code></td> <td>Less than or equal to</td> <td>Tests whether the left value is smaller than or equal to the right one.</td> <td><code>3 <= 2</code></td> </tr> <tr> <td><code>>=</code></td> <td>Greater than or equal to</td> <td>Tests whether the left value is greater than or equal to the right one.</td> <td><code>5 >= 4</code></td> </tr> </tbody> </table> </figure> <div class="notecard note"> <p><strong>Note:</strong> You may see some people using <code>==</code> and <code>!=</code> in their tests for equality and non-equality. These are valid operators in JavaScript, but they differ from <code>===</code>/<code>!==</code>. The former versions test whether the values are the same but not whether the values' datatypes are the same. The latter, strict versions test the equality of both the values and their datatypes. The strict versions tend to result in fewer errors, so we recommend you use them.</p> </div> <p>If you try entering some of these values in a console, you'll see that they all return <code>true</code>/<code>false</code> values — those booleans we mentioned in the last article. These are very useful, as they allow us to make decisions in our code, and they are used every time we want to make a choice of some kind. For example, booleans can be used to:</p> <ul> <li>Display the correct text label on a button depending on whether a feature is turned on or off</li> <li>Display a game over message if a game is over or a victory message if the game has been won</li> <li>Display the correct seasonal greeting depending on what holiday season it is</li> <li>Zoom a map in or out depending on what zoom level is selected</li> </ul> <p>We'll look at how to code such logic when we look at conditional statements in a future article. For now, let's look at a quick example:</p> <div class="code-example"> <div class="example-header"> <span class="language-name">html</span> </div> <pre class="brush: html notranslate"><code><button>Start machine</button> <p>The machine is stopped.</p> </code></pre> </div> <div class="code-example"> <div class="example-header"> <span class="language-name">js</span> </div> <pre class="brush: js notranslate"><code>const btn = document.querySelector("button"); const txt = document.querySelector("p"); btn.addEventListener("click", updateBtn); function updateBtn() { if (btn.textContent === "Start machine") { btn.textContent = "Stop machine"; txt.textContent = "The machine has started!"; } else { btn.textContent = "Start machine"; txt.textContent = "The machine is stopped."; } } </code></pre> </div><iframe width="100%" height="100" src="https://mdn.github.io/learning-area/javascript/introduction-to-js-1/maths/conditional.html" loading="lazy"></iframe> <p><strong><a href="https://translate.google.com/website?sl=pl&tl=fr&hl=en-GB&u=https://mdn.github.io/learning-area/javascript/introduction-to-js-1/maths/conditional.html" class="external" target="_blank">Open in new window</a></strong></p> <p>You can see the equality operator being used just inside the <code>updateBtn()</code> function. In this case, we are not testing if two mathematical expressions have the same value — we are testing whether the text content of a button contains a certain string — but it is still the same principle at work. If the button is currently saying "Start machine" when it is pressed, we change its label to "Stop machine", and update the label as appropriate. If the button is currently saying "Stop machine" when it is pressed, we swap the display back again.</p> <div class="notecard note"> <p><strong>Note:</strong> Such a control that swaps between two states is generally referred to as a <strong>toggle</strong>. It toggles between one state and another — light on, light off, etc.</p> </div> </div> </section> <section aria-labelledby="test_your_skills!"> <h2 id="test_your_skills!"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#test_your_skills!">Test your skills!</a></h2> <div class="section-content"> <p>You've reached the end of this article, but can you remember the most important information? You can find some further tests to verify that you've retained this information before you move on — see <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Test_your_skills:_Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Test your skills: Math</a>.</p> </div> </section> <section aria-labelledby="summary"> <h2 id="summary"><a href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Math?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB#summary">Summary</a></h2> <div class="section-content"> <p>In this article, we have covered the fundamental information you need to know about numbers in JavaScript, for now. You'll see numbers used again and again, all the way through your JavaScript learning, so it's a good idea to get this out of the way now. If you are one of those people that doesn't enjoy math, you can take comfort in the fact that this chapter was pretty short.</p> <p>In the next article, we'll explore text and how JavaScript allows us to manipulate it.</p> <div class="notecard note"> <p><strong>Note:</strong> If you do enjoy math and want to read more about how it is implemented in JavaScript, you can find a lot more detail in MDN's main JavaScript section. Great places to start are our <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Guide/Numbers_and_dates?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Numbers and dates</a> and <a href="https://developer-mozilla-org.translate.goog/en-US/docs/Web/JavaScript/Guide/Expressions_and_operators?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">Expressions and operators</a> articles.</p> </div> <ul class="prev-next"> <li><a class="button secondary" href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps/Variables?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB"><span class="button-wrap"> Previous </span></a></li> <li><a class="button secondary" href="https://developer-mozilla-org.translate.goog/en-US/docs/Learn/JavaScript/First_steps?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB"><span class="button-wrap"> Overview: JavaScript first steps</span></a></li> <li><a class="button secondary" 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target="_blank" rel="noopener noreferrer">Mozilla Corporation’s</a> not-for-profit parent, the <a target="_blank" rel="noopener noreferrer" href="https://translate.google.com/website?sl=pl&tl=fr&hl=en-GB&u=https://foundation.mozilla.org/">Mozilla Foundation</a>.<br> Portions of this content are ©1998–2024 by individual mozilla.org contributors. Content available under <a href="https://developer-mozilla-org.translate.goog/en-US/docs/MDN/Writing_guidelines/Attrib_copyright_license?_x_tr_sl=pl&_x_tr_tl=fr&_x_tr_hl=en-GB">a Creative Commons license</a>.</p> </div> </div> </footer> </div> <script type="application/json" id="hydration">{"url":"/en-US/docs/Learn/JavaScript/First_steps/Math","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/JavaScript/First_steps/Variables\"><span class=\"button-wrap\"> Previous </span></a></li><li><a class=\"button secondary\" href=\"/en-US/docs/Learn/JavaScript/First_steps\"><span class=\"button-wrap\"> Overview: JavaScript first steps</span></a></li><li><a class=\"button secondary\" href=\"/en-US/docs/Learn/JavaScript/First_steps/Strings\"><span class=\"button-wrap\"> Next </span></a></li></ul>\n<p>At this point in the course, we discuss math in JavaScript — how we can use <a href=\"/en-US/docs/Glossary/Operator\">operators</a> and other features to successfully manipulate numbers to do our bidding.</p>\n<figure class=\"table-container\"><table>\n <tbody>\n <tr>\n <th scope=\"row\">Prerequisites:</th>\n <td>\n A basic understanding of HTML and CSS, an\n understanding of what JavaScript is.\n </td>\n </tr>\n <tr>\n <th scope=\"row\">Objective:</th>\n <td>To gain familiarity with the basics of math in JavaScript.</td>\n </tr>\n </tbody>\n</table></figure>"}},{"type":"prose","value":{"id":"everybody_loves_math","title":"Everybody loves math","isH3":false,"content":"<p>Okay, maybe not. Some of us like math, some of us have hated math ever since we had to learn multiplication tables and long division in school, and some of us sit somewhere in between the two. But none of us can deny that math is a fundamental part of life that we can't get very far without. This is especially true when we are learning to program JavaScript (or any other language for that matter) — so much of what we do relies on processing numerical data, calculating new values, and so on, that you won't be surprised to learn that JavaScript has a full-featured set of math functions available.</p>\n<p>This article discusses only the basic parts that you need to know now.</p>"}},{"type":"prose","value":{"id":"types_of_numbers","title":"Types of numbers","isH3":true,"content":"<p>In programming, even the humble decimal number system that we all know so well is more complicated than you might think. We use different terms to describe different types of decimal numbers, for example:</p>\n<ul>\n<li><strong>Integers</strong> are numbers without a fractional part. They can either be positive or negative, e.g. 10, 400, or -5.</li>\n<li><strong>Floating point numbers</strong> (floats) have decimal points and decimal places, for example 12.5, and 56.7786543.</li>\n</ul>\n<p>We even have different types of number systems! Decimal is base 10 (meaning it uses 0–9 in each digit), but we also have things like:</p>\n<ul>\n<li><strong>Binary</strong> — The lowest level language of computers; 0s and 1s.</li>\n<li><strong>Octal</strong> — Base 8, uses 0–7 in each digit.</li>\n<li><strong>Hexadecimal</strong> — Base 16, uses 0–9 and then a–f in each digit. You may have encountered these numbers before when setting <a href=\"/en-US/docs/Learn/CSS/Building_blocks/Values_and_units#hexadecimal_rgb_values\">colors in CSS</a>.</li>\n</ul>\n<p><strong>Before you start to get worried about your brain melting, stop right there!</strong> For a start, we are just going to stick to decimal numbers throughout this course; you'll rarely come across a need to start thinking about other types, if ever.</p>\n<p>The second bit of good news is that unlike some other programming languages, JavaScript only has one data type for numbers, both integers and decimals — you guessed it, <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number\"><code>Number</code></a>. This means that whatever type of numbers you are dealing with in JavaScript, you handle them in exactly the same way.</p>\n<div class=\"notecard note\">\n<p><strong>Note:</strong>\nActually, JavaScript has a second number type, <a href=\"/en-US/docs/Glossary/BigInt\">BigInt</a>, used for very, very large integers. But for the purposes of this course, we'll just worry about <code>Number</code> values.</p>\n</div>"}},{"type":"prose","value":{"id":"its_all_numbers_to_me","title":"It's all numbers to me","isH3":true,"content":"<p>Let's quickly play with some numbers to reacquaint ourselves with the basic syntax we need. Enter the commands listed below into your <a href=\"/en-US/docs/Learn/Common_questions/Tools_and_setup/What_are_browser_developer_tools\">developer tools JavaScript console</a>.</p>\n<ol>\n<li>\n<p>First of all, let's declare a couple of variables and initialize them with an integer and a float, respectively, then type the variable names back in to check that everything is in order:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>const myInt = 5;\nconst myFloat = 6.667;\nmyInt;\nmyFloat;\n</code></pre></div>\n</li>\n<li>\n<p>Number values are typed in without quote marks — try declaring and initializing a couple more variables containing numbers before you move on.</p>\n</li>\n<li>\n<p>Now let's check that both our original variables are of the same datatype. There is an operator called <a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/typeof\"><code>typeof</code></a> in JavaScript that does this. Enter the below two lines as shown:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>typeof myInt;\ntypeof myFloat;\n</code></pre></div>\n<p>You should get <code>\"number\"</code> returned in both cases — this makes things a lot easier for us than if different numbers had different data types, and we had to deal with them in different ways. Phew!</p>\n</li>\n</ol>"}},{"type":"prose","value":{"id":"useful_number_methods","title":"Useful Number methods","isH3":true,"content":"<p>The <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number\"><code>Number</code></a> object, an instance of which represents all standard numbers you'll use in your JavaScript, has a number of useful methods available on it for you to manipulate numbers. We don't cover these in detail in this article because we wanted to keep it as an introduction and only cover the real basic essentials for now; however, once you've read through this module a couple of times it is worth going to the object reference pages and learning more about what's available.</p>\n<p>For example, to round your number to a fixed number of decimal places, use the <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/toFixed\"><code>toFixed()</code></a> method. Type the following lines into your browser's <a href=\"https://firefox-source-docs.mozilla.org/devtools-user/web_console/index.html\" class=\"external\" target=\"_blank\">console</a>:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>const lotsOfDecimal = 1.766584958675746364;\nlotsOfDecimal;\nconst twoDecimalPlaces = lotsOfDecimal.toFixed(2);\ntwoDecimalPlaces;\n</code></pre></div>"}},{"type":"prose","value":{"id":"converting_to_number_data_types","title":"Converting to number data types","isH3":true,"content":"<p>Sometimes you might end up with a number that is stored as a string type, which makes it difficult to perform calculations with it. This most commonly happens when data is entered into a <a href=\"/en-US/docs/Learn/Forms\">form</a> input, and the <a href=\"/en-US/docs/Web/HTML/Element/input/text\">input type is text</a>. There is a way to solve this problem — passing the string value into the <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/Number\"><code>Number()</code></a> constructor to return a number version of the same value.</p>\n<p>For example, try typing these lines into your console:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>let myNumber = \"74\";\nmyNumber += 3;\n</code></pre></div>\n<p>You end up with the result 743, not 77, because <code>myNumber</code> is actually defined as a string. You can test this by typing in 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>typeof myNumber;\n</code></pre></div>\n<p>To fix the calculation, you can do this:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>let myNumber = \"74\";\nmyNumber = Number(myNumber) + 3;\n</code></pre></div>\n<p>The result is then 77, as initially expected.</p>"}},{"type":"prose","value":{"id":"arithmetic_operators","title":"Arithmetic operators","isH3":false,"content":"<p>Arithmetic operators are used for performing mathematical calculations in JavaScript:</p>\n<figure class=\"table-container\"><table class=\"standard-table\">\n <thead>\n <tr>\n <th scope=\"col\">Operator</th>\n <th scope=\"col\">Name</th>\n <th scope=\"col\">Purpose</th>\n <th scope=\"col\">Example</th>\n </tr>\n </thead>\n <tbody>\n <tr>\n <td><code>+</code></td>\n <td>Addition</td>\n <td>Adds two numbers together.</td>\n <td><code>6 + 9</code></td>\n </tr>\n <tr>\n <td><code>-</code></td>\n <td>Subtraction</td>\n <td>Subtracts the right number from the left.</td>\n <td><code>20 - 15</code></td>\n </tr>\n <tr>\n <td><code>*</code></td>\n <td>Multiplication</td>\n <td>Multiplies two numbers together.</td>\n <td><code>3 * 7</code></td>\n </tr>\n <tr>\n <td><code>/</code></td>\n <td>Division</td>\n <td>Divides the left number by the right.</td>\n <td><code>10 / 5</code></td>\n </tr>\n <tr>\n <td><code>%</code></td>\n <td>Remainder (sometimes called modulo)</td>\n <td>\n <p>\n Returns the remainder left over after you've divided the left number\n into a number of integer portions equal to the right number.\n </p>\n </td>\n <td>\n <p>\n <code>8 % 3</code> (returns 2, as three goes into 8 twice, leaving 2\n left over).\n </p>\n </td>\n </tr>\n <tr>\n <td><code>**</code></td>\n <td>Exponent</td>\n <td>\n Raises a <code>base</code> number to the <code>exponent</code> power,\n that is, the <code>base</code> number multiplied by itself,\n <code>exponent</code> times.\n </td>\n <td>\n <code>5 ** 2</code> (returns <code>25</code>, which is the same as\n <code>5 * 5</code>).\n </td>\n </tr>\n </tbody>\n</table></figure>\n<div class=\"notecard note\">\n<p><strong>Note:</strong>\nYou'll sometimes see numbers involved in arithmetic referred to as <a href=\"/en-US/docs/Glossary/Operand\">operands</a>.</p>\n</div>\n<div class=\"notecard note\">\n<p><strong>Note:</strong>\nYou may sometimes see exponents expressed using the older <a href=\"/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/pow\"><code>Math.pow()</code></a> method, which works in a very similar way. For example, in <code>Math.pow(7, 3)</code>, <code>7</code> is the base and <code>3</code> is the exponent, so the result of the expression is <code>343</code>. <code>Math.pow(7, 3)</code> is equivalent to <code>7**3</code>.</p>\n</div>\n<p>We probably don't need to teach you how to do basic math, but we would like to test your understanding of the syntax involved. Try entering the examples below into your <a href=\"/en-US/docs/Learn/Common_questions/Tools_and_setup/What_are_browser_developer_tools\">developer tools JavaScript console</a> to familiarize yourself with the syntax.</p>\n<ol>\n<li>\n<p>First try entering some simple examples of your own, such as</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>10 + 7;\n9 * 8;\n60 % 3;\n</code></pre></div>\n</li>\n<li>\n<p>You can also try declaring and initializing some numbers inside variables, and try using those in the sums — the variables will behave exactly like the values they hold for the purposes of the sum. For example:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>const num1 = 10;\nconst num2 = 50;\n9 * num1;\nnum1 ** 3;\nnum2 / num1;\n</code></pre></div>\n</li>\n<li>\n<p>Last for this section, try entering some more complex expressions, such as:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>5 + 10 * 3;\n(num2 % 9) * num1;\nnum2 + num1 / 8 + 2;\n</code></pre></div>\n</li>\n</ol>\n<p>Parts of this last set of calculations might not give you quite the result you were expecting; the section below might well give the answer as to why.</p>"}},{"type":"prose","value":{"id":"operator_precedence","title":"Operator precedence","isH3":true,"content":"<p>Let's look at the last example from above, assuming that <code>num2</code> holds the value 50 and <code>num1</code> holds the value 10 (as originally stated above):</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>num2 + num1 / 8 + 2;\n</code></pre></div>\n<p>As a human being, you may read this as <em>\"50 plus 10 equals 60\"</em>, then <em>\"8 plus 2 equals 10\"</em>, and finally <em>\"60 divided by 10 equals 6\"</em>.</p>\n<p>But the browser does <em>\"10 divided by 8 equals 1.25\"</em>, then <em>\"50 plus 1.25 plus 2 equals 53.25\"</em>.</p>\n<p>This is because of <strong>operator precedence</strong> — some operators are applied before others when calculating the result of a calculation (referred to as an <em>expression</em>, in programming). Operator precedence in JavaScript is the same as is taught in math classes in school — multiply and divide are always done first, then add and subtract (the calculation is always evaluated from left to right).</p>\n<p>If you want to override operator precedence, you can put parentheses around the parts that you want to be explicitly dealt with first. So to get a result of 6, we could do this:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>(num2 + num1) / (8 + 2);\n</code></pre></div>\n<p>Try it and see.</p>\n<div class=\"notecard note\">\n<p><strong>Note:</strong>\nA full list of all JavaScript operators and their precedence can be found in <a href=\"/en-US/docs/Web/JavaScript/Reference/Operators/Operator_precedence\">Operator precedence</a>.</p>\n</div>"}},{"type":"prose","value":{"id":"increment_and_decrement_operators","title":"Increment and decrement operators","isH3":false,"content":"<p>Sometimes you'll want to repeatedly add or subtract one to or from a numeric variable value. This can be conveniently done using the increment (<code>++</code>) and decrement (<code>--</code>) operators. We used <code>++</code> in our \"Guess the number\" game back in our <a href=\"/en-US/docs/Learn/JavaScript/First_steps/A_first_splash\">first splash into JavaScript</a> article, when we added 1 to our <code>guessCount</code> variable to keep track of how many guesses the user has left after each turn.</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>guessCount++;\n</code></pre></div>\n<p>Let's try playing with these in your console. For a start, note that you can't apply these directly to a number, which might seem strange, but we are assigning a variable a new updated value, not operating on the value itself. The following will return an error:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js example-bad notranslate\"><code>3++;\n</code></pre></div>\n<p>So, you can only increment an existing variable. Try this:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>let num1 = 4;\nnum1++;\n</code></pre></div>\n<p>Okay, strangeness number 2! When you do this, you'll see a value of 4 returned — this is because the browser returns the current value, <em>then</em> increments the variable. You can see that it's been incremented if you return the variable value again:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>num1;\n</code></pre></div>\n<p>The same is true of <code>--</code> : try 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>let num2 = 6;\nnum2--;\nnum2;\n</code></pre></div>\n<div class=\"notecard note\">\n<p><strong>Note:</strong>\nYou can make the browser do it the other way round — increment/decrement the variable <em>then</em> return the value — by putting the operator at the start of the variable instead of the end. Try the above examples again, but this time use <code>++num1</code> and <code>--num2</code>.</p>\n</div>"}},{"type":"prose","value":{"id":"assignment_operators","title":"Assignment operators","isH3":false,"content":"<p>Assignment operators are operators that assign a value to a variable. We have already used the most basic one, <code>=</code>, loads of times — it assigns the variable on the left the value stated on the right:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>let x = 3; // x contains the value 3\nlet y = 4; // y contains the value 4\nx = y; // x now contains the same value y contains, 4\n</code></pre></div>\n<p>But there are some more complex types, which provide useful shortcuts to keep your code neater and more efficient. The most common are listed below:</p>\n<figure class=\"table-container\"><table class=\"standard-table no-markdown\">\n <thead>\n <tr>\n <th scope=\"col\">Operator</th>\n <th scope=\"col\">Name</th>\n <th scope=\"col\">Purpose</th>\n <th scope=\"col\">Example</th>\n <th scope=\"col\">Shortcut for</th>\n </tr>\n </thead>\n <tbody>\n <tr>\n <td><code>+=</code></td>\n <td>Addition assignment</td>\n <td>\n Adds the value on the right to the variable value on the left, then\n returns the new variable value\n </td>\n <td><code>x += 4;</code></td>\n <td><code>x = x + 4;</code></td>\n </tr>\n <tr>\n <td><code>-=</code></td>\n <td>Subtraction assignment</td>\n <td>\n Subtracts the value on the right from the variable value on the left,\n and returns the new variable value\n </td>\n <td><code>x -= 3;</code></td>\n <td><code>x = x - 3;</code></td>\n </tr>\n <tr>\n <td><code>*=</code></td>\n <td>Multiplication assignment</td>\n <td>\n Multiplies the variable value on the left by the value on the right, and\n returns the new variable value\n </td>\n <td><code>x *= 3;</code></td>\n <td><code>x = x * 3;</code></td>\n </tr>\n <tr>\n <td><code>/=</code></td>\n <td>Division assignment</td>\n <td>\n Divides the variable value on the left by the value on the right, and\n returns the new variable value\n </td>\n <td><code>x /= 5;</code></td>\n <td><code>x = x / 5;</code></td>\n </tr>\n </tbody>\n</table></figure>\n<p>Try typing some of the above examples into your console, to get an idea of how they work. In each case, see if you can guess what the value is before you type in the second line.</p>\n<p>Note that you can quite happily use other variables on the right-hand side of each expression, for example:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>let x = 3; // x contains the value 3\nlet y = 4; // y contains the value 4\nx *= y; // x now contains the value 12\n</code></pre></div>\n<div class=\"notecard note\">\n<p><strong>Note:</strong>\nThere are lots of <a href=\"/en-US/docs/Web/JavaScript/Guide/Expressions_and_operators#assignment_operators\">other assignment operators available</a>, but these are the basic ones you should learn now.</p>\n</div>"}},{"type":"prose","value":{"id":"active_learning_sizing_a_canvas_box","title":"Active learning: sizing a canvas box","isH3":false,"content":"<p>In this exercise, you will manipulate some numbers and operators to change the size of a box. The box is drawn using a browser API called the <a href=\"/en-US/docs/Web/API/Canvas_API\">Canvas API</a>. There is no need to worry about how this works — just concentrate on the math for now. The width and height of the box (in pixels) are defined by the variables <code>x</code> and <code>y</code>, which are initially both given a value of 50.</p>\n<iframe width=\"100%\" height=\"620\" src=\"https://mdn.github.io/learning-area/javascript/introduction-to-js-1/maths/editable_canvas.html\" loading=\"lazy\"></iframe>\n<p><strong><a href=\"https://mdn.github.io/learning-area/javascript/introduction-to-js-1/maths/editable_canvas.html\" class=\"external\" target=\"_blank\">Open in new window</a></strong></p>\n<p>In the editable code box above, there are two lines marked with a comment that we'd like you to update to make the box grow/shrink to certain sizes, using certain operators and/or values in each case. Let's try the following:</p>\n<ul>\n<li>Change the line that calculates x so the box is still 50px wide, but the 50 is calculated using the numbers 43 and 7 and an arithmetic operator.</li>\n<li>Change the line that calculates y so the box is 75px high, but the 75 is calculated using the numbers 25 and 3 and an arithmetic operator.</li>\n<li>Change the line that calculates x so the box is 250px wide, but the 250 is calculated using two numbers and the remainder (modulo) operator.</li>\n<li>Change the line that calculates y so the box is 150px high, but the 150 is calculated using three numbers and the subtraction and division operators.</li>\n<li>Change the line that calculates x so the box is 200px wide, but the 200 is calculated using the number 4 and an assignment operator.</li>\n<li>Change the line that calculates y so the box is 200px high, but the 200 is calculated using the numbers 50 and 3, the multiplication operator, and the addition assignment operator.</li>\n</ul>\n<p>Don't worry if you totally mess the code up. You can always press the Reset button to get things working again. After you've answered all the above questions correctly, feel free to play with the code some more or create your own challenges.</p>"}},{"type":"prose","value":{"id":"comparison_operators","title":"Comparison operators","isH3":false,"content":"<p>Sometimes we will want to run true/false tests, then act accordingly depending on the result of that test — to do this we use <strong>comparison operators</strong>.</p>\n<figure class=\"table-container\"><table>\n<thead>\n<tr>\n<th>Operator</th>\n<th>Name</th>\n<th>Purpose</th>\n<th>Example</th>\n</tr>\n</thead>\n<tbody>\n<tr>\n<td><code>===</code></td>\n<td>Strict equality</td>\n<td>Tests whether the left and right values are identical to one another</td>\n<td><code>5 === 2 + 4</code></td>\n</tr>\n<tr>\n<td><code>!==</code></td>\n<td>Strict-non-equality</td>\n<td>Tests whether the left and right values are <strong>not</strong> identical to one another</td>\n<td><code>5 !== 2 + 3</code></td>\n</tr>\n<tr>\n<td><code><</code></td>\n<td>Less than</td>\n<td>Tests whether the left value is smaller than the right one.</td>\n<td><code>10 < 6</code></td>\n</tr>\n<tr>\n<td><code>></code></td>\n<td>Greater than</td>\n<td>Tests whether the left value is greater than the right one.</td>\n<td><code>10 > 20</code></td>\n</tr>\n<tr>\n<td><code><=</code></td>\n<td>Less than or equal to</td>\n<td>Tests whether the left value is smaller than or equal to the right one.</td>\n<td><code>3 <= 2</code></td>\n</tr>\n<tr>\n<td><code>>=</code></td>\n<td>Greater than or equal to</td>\n<td>Tests whether the left value is greater than or equal to the right one.</td>\n<td><code>5 >= 4</code></td>\n</tr>\n</tbody>\n</table></figure>\n<div class=\"notecard note\">\n<p><strong>Note:</strong>\nYou may see some people using <code>==</code> and <code>!=</code> in their tests for equality and non-equality. These are valid operators in JavaScript, but they differ from <code>===</code>/<code>!==</code>. The former versions test whether the values are the same but not whether the values' datatypes are the same. The latter, strict versions test the equality of both the values and their datatypes. The strict versions tend to result in fewer errors, so we recommend you use them.</p>\n</div>\n<p>If you try entering some of these values in a console, you'll see that they all return <code>true</code>/<code>false</code> values — those booleans we mentioned in the last article. These are very useful, as they allow us to make decisions in our code, and they are used every time we want to make a choice of some kind. For example, booleans can be used to:</p>\n<ul>\n<li>Display the correct text label on a button depending on whether a feature is turned on or off</li>\n<li>Display a game over message if a game is over or a victory message if the game has been won</li>\n<li>Display the correct seasonal greeting depending on what holiday season it is</li>\n<li>Zoom a map in or out depending on what zoom level is selected</li>\n</ul>\n<p>We'll look at how to code such logic when we look at conditional statements in a future article. For now, let's look at a quick example:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">html</span></div><pre class=\"brush: html notranslate\"><code><button>Start machine</button>\n<p>The machine is stopped.</p>\n</code></pre></div>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>const btn = document.querySelector(\"button\");\nconst txt = document.querySelector(\"p\");\n\nbtn.addEventListener(\"click\", updateBtn);\n\nfunction updateBtn() {\n if (btn.textContent === \"Start machine\") {\n btn.textContent = \"Stop machine\";\n txt.textContent = \"The machine has started!\";\n } else {\n btn.textContent = \"Start machine\";\n txt.textContent = \"The machine is stopped.\";\n }\n}\n</code></pre></div>\n<iframe width=\"100%\" height=\"100\" src=\"https://mdn.github.io/learning-area/javascript/introduction-to-js-1/maths/conditional.html\" loading=\"lazy\"></iframe>\n<p><strong><a href=\"https://mdn.github.io/learning-area/javascript/introduction-to-js-1/maths/conditional.html\" class=\"external\" target=\"_blank\">Open in new window</a></strong></p>\n<p>You can see the equality operator being used just inside the <code>updateBtn()</code> function. In this case, we are not testing if two mathematical expressions have the same value — we are testing whether the text content of a button contains a certain string — but it is still the same principle at work. If the button is currently saying \"Start machine\" when it is pressed, we change its label to \"Stop machine\", and update the label as appropriate. If the button is currently saying \"Stop machine\" when it is pressed, we swap the display back again.</p>\n<div class=\"notecard note\">\n<p><strong>Note:</strong>\nSuch a control that swaps between two states is generally referred to as a <strong>toggle</strong>. It toggles between one state and another — light on, light off, etc.</p>\n</div>"}},{"type":"prose","value":{"id":"test_your_skills!","title":"Test your skills!","isH3":false,"content":"<p>You've reached the end of this article, but can you remember the most important information? You can find some further tests to verify that you've retained this information before you move on — see <a href=\"/en-US/docs/Learn/JavaScript/First_steps/Test_your_skills:_Math\">Test your skills: Math</a>.</p>"}},{"type":"prose","value":{"id":"summary","title":"Summary","isH3":false,"content":"<p>In this article, we have covered the fundamental information you need to know about numbers in JavaScript, for now. You'll see numbers used again and again, all the way through your JavaScript learning, so it's a good idea to get this out of the way now. If you are one of those people that doesn't enjoy math, you can take comfort in the fact that this chapter was pretty short.</p>\n<p>In the next article, we'll explore text and how JavaScript allows us to manipulate it.</p>\n<div class=\"notecard note\">\n<p><strong>Note:</strong>\nIf you do enjoy math and want to read more about how it is implemented in JavaScript, you can find a lot more detail in MDN's main JavaScript section. Great places to start are our <a href=\"/en-US/docs/Web/JavaScript/Guide/Numbers_and_dates\">Numbers and dates</a> and <a href=\"/en-US/docs/Web/JavaScript/Guide/Expressions_and_operators\">Expressions and operators</a> articles.</p>\n</div>\n<ul class=\"prev-next\"><li><a class=\"button secondary\" href=\"/en-US/docs/Learn/JavaScript/First_steps/Variables\"><span class=\"button-wrap\"> Previous </span></a></li><li><a class=\"button secondary\" href=\"/en-US/docs/Learn/JavaScript/First_steps\"><span class=\"button-wrap\"> Overview: JavaScript first steps</span></a></li><li><a class=\"button secondary\" href=\"/en-US/docs/Learn/JavaScript/First_steps/Strings\"><span class=\"button-wrap\"> Next </span></a></li></ul>"}}],"isActive":true,"isMarkdown":true,"isTranslated":false,"locale":"en-US","mdn_url":"/en-US/docs/Learn/JavaScript/First_steps/Math","modified":"2024-11-21T19:49:47.000Z","native":"English (US)","noIndexing":false,"other_translations":[{"locale":"de","title":"Grundlegende Mathematik in JavaScript – Zahlen und Operatoren","native":"Deutsch"},{"locale":"es","title":"Matemáticas básicas en JavaScript — números y operadores","native":"Español"},{"locale":"fr","title":"Mathématiques de base en JavaScript — nombres et opérateurs","native":"Français"},{"locale":"ja","title":"JavaScript での基本演算 — 数値と演算子","native":"日本語"},{"locale":"ko","title":"JavaScript의 기본적인 연산 - 숫자와 연산자","native":"한국어"},{"locale":"pt-BR","title":"Matemática básica no JavaScript — números e operadores","native":"Português (do Brasil)"},{"locale":"ru","title":"Базовая математика в JavaScript — числа и операторы","native":"Русский"},{"locale":"zh-CN","title":"JavaScript 中的基础数学 — 数字和操作符","native":"中文 (简体)"},{"locale":"zh-TW","title":"JavaScript中的基本數學 - 數字和運算符","native":"正體中文 (繁體)"}],"pageTitle":"Basic math in JavaScript — numbers and operators - Learn web development | MDN","parents":[{"uri":"/en-US/docs/Learn","title":"Guides"},{"uri":"/en-US/docs/Learn/JavaScript","title":"JavaScript — Dynamic client-side scripting"},{"uri":"/en-US/docs/Learn/JavaScript/First_steps","title":"JavaScript first steps"},{"uri":"/en-US/docs/Learn/JavaScript/First_steps/Math","title":"Basic math in JavaScript — numbers and operators"}],"popularity":null,"short_title":"Basic math in JavaScript — numbers and operators","sidebarHTML":"<ol><li class=\"section\"><a href=\"/en-US/docs/Learn/Getting_started_with_the_web\">Complete beginners start here!</a></li><li class=\"toggle\"><details><summary>Getting started with the web</summary><ol><li><a href=\"/en-US/docs/Learn/Getting_started_with_the_web\">Getting started with the web</a></li><li><a href=\"/en-US/docs/Learn/Getting_started_with_the_web/Installing_basic_software\">Installing basic software</a></li><li><a href=\"/en-US/docs/Learn/Getting_started_with_the_web/What_will_your_website_look_like\">What will your website look like?</a><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n<span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Learn/Getting_started_with_the_web/Dealing_with_files\">Dealing with files</a></li><li><a href=\"/en-US/docs/Learn/Getting_started_with_the_web/HTML_basics\">HTML basics</a></li><li><a href=\"/en-US/docs/Learn/Getting_started_with_the_web/CSS_basics\">CSS basics</a></li><li><a href=\"/en-US/docs/Learn/Getting_started_with_the_web/JavaScript_basics\">JavaScript basics</a></li><li><a href=\"/en-US/docs/Learn/Getting_started_with_the_web/Publishing_your_website\">Publishing your website</a></li><li><a href=\"/en-US/docs/Learn/Getting_started_with_the_web/How_the_Web_works\">How the web works</a></li></ol></details></li><li class=\"section\"><a href=\"/en-US/docs/Learn/HTML\">HTML — Structuring the web</a></li><li class=\"toggle\"><details><summary>Introduction to HTML</summary><ol><li><a href=\"/en-US/docs/Learn/HTML/Introduction_to_HTML\">Introduction to HTML</a></li><li><a href=\"/en-US/docs/Learn/HTML/Introduction_to_HTML/Getting_started\">Getting started with HTML</a></li><li><a href=\"/en-US/docs/Learn/HTML/Introduction_to_HTML/The_head_metadata_in_HTML\">What's in the head? Metadata in HTML</a></li><li><a href=\"/en-US/docs/Learn/HTML/Introduction_to_HTML/HTML_text_fundamentals\">HTML text fundamentals</a></li><li><a href=\"/en-US/docs/Learn/HTML/Introduction_to_HTML/Creating_hyperlinks\">Creating hyperlinks</a></li><li><a href=\"/en-US/docs/Learn/HTML/Introduction_to_HTML/Advanced_text_formatting\">Advanced text formatting</a></li><li><a href=\"/en-US/docs/Learn/HTML/Introduction_to_HTML/Document_and_website_structure\">Document and website structure</a></li><li><a href=\"/en-US/docs/Learn/HTML/Introduction_to_HTML/Debugging_HTML\">Debugging HTML</a></li><li><a href=\"/en-US/docs/Learn/HTML/Introduction_to_HTML/Marking_up_a_letter\">Marking up a letter</a></li><li><a href=\"/en-US/docs/Learn/HTML/Introduction_to_HTML/Structuring_a_page_of_content\">Structuring a page of content</a></li></ol></details></li><li class=\"toggle\"><details><summary>Multimedia and embedding</summary><ol><li><a href=\"/en-US/docs/Learn/HTML/Multimedia_and_embedding\">Multimedia and embedding</a></li><li><a href=\"/en-US/docs/Learn/HTML/Multimedia_and_embedding/Images_in_HTML\">Images in HTML</a></li><li><a href=\"/en-US/docs/Learn/HTML/Multimedia_and_embedding/Video_and_audio_content\">Video and audio content</a></li><li><a href=\"/en-US/docs/Learn/HTML/Multimedia_and_embedding/Other_embedding_technologies\">From object to iframe — other embedding technologies</a></li><li><a href=\"/en-US/docs/Learn/HTML/Multimedia_and_embedding/Adding_vector_graphics_to_the_Web\">Adding vector graphics to the web</a></li><li><a href=\"/en-US/docs/Learn/HTML/Multimedia_and_embedding/Responsive_images\">Responsive images</a></li><li><a href=\"/en-US/docs/Learn/HTML/Multimedia_and_embedding/Mozilla_splash_page\">Mozilla splash page</a></li></ol></details></li><li class=\"toggle\"><details><summary>HTML tables</summary><ol><li><a href=\"/en-US/docs/Learn/HTML/Tables\">HTML tables</a></li><li><a href=\"/en-US/docs/Learn/HTML/Tables/Basics\">HTML table basics</a></li><li><a href=\"/en-US/docs/Learn/HTML/Tables/Advanced\">HTML table advanced features and accessibility</a></li><li><a href=\"/en-US/docs/Learn/HTML/Tables/Structuring_planet_data\">Structuring planet data</a></li></ol></details></li><li class=\"section\"><a href=\"/en-US/docs/Learn/CSS\">CSS — Styling the web</a></li><li class=\"toggle\"><details><summary>CSS first steps</summary><ol><li><a href=\"/en-US/docs/Learn/CSS/First_steps\">CSS first steps</a></li><li><a href=\"/en-US/docs/Learn/CSS/First_steps/What_is_CSS\">What is CSS?</a></li><li><a href=\"/en-US/docs/Learn/CSS/First_steps/Getting_started\">Getting started with CSS</a></li><li><a href=\"/en-US/docs/Learn/CSS/First_steps/How_CSS_is_structured\">How CSS is structured</a></li><li><a href=\"/en-US/docs/Learn/CSS/First_steps/How_CSS_works\">How CSS works</a></li><li><a href=\"/en-US/docs/Learn/CSS/First_steps/Styling_a_biography_page\">Styling a biography page</a></li></ol></details></li><li class=\"toggle\"><details><summary>CSS building blocks</summary><ol><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks\">CSS building blocks</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Selectors\">CSS selectors</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Selectors/Type_Class_and_ID_Selectors\">Type, class, and ID selectors</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Selectors/Attribute_selectors\">Attribute selectors</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Selectors/Pseudo-classes_and_pseudo-elements\">Pseudo-classes and pseudo-elements</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Selectors/Combinators\">Combinators</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Cascade_and_inheritance\">Cascade, specificity, and inheritance</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Cascade_layers\">Cascade layers</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/The_box_model\">The box model</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Backgrounds_and_borders\">Backgrounds and borders</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Handling_different_text_directions\">Handling different text directions</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Overflowing_content\">Overflowing content</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Values_and_units\">CSS values and units</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Sizing_items_in_CSS\">Sizing items in CSS</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Images_media_form_elements\">Images, media, and form elements</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Styling_tables\">Styling tables</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Advanced_styling_effects\">Advanced styling effects</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Debugging_CSS\">Debugging CSS</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Organizing\">Organizing your CSS</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Fundamental_CSS_comprehension\">Fundamental CSS comprehension</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/Creating_fancy_letterheaded_paper\">Creating fancy letterheaded paper</a></li><li><a href=\"/en-US/docs/Learn/CSS/Building_blocks/A_cool_looking_box\">A cool-looking box</a></li></ol></details></li><li class=\"toggle\"><details><summary>Styling text</summary><ol><li><a href=\"/en-US/docs/Learn/CSS/Styling_text\">CSS styling text</a></li><li><a href=\"/en-US/docs/Learn/CSS/Styling_text/Fundamentals\">Fundamental text and font styling</a></li><li><a href=\"/en-US/docs/Learn/CSS/Styling_text/Styling_lists\">Styling lists</a></li><li><a href=\"/en-US/docs/Learn/CSS/Styling_text/Styling_links\">Styling links</a></li><li><a href=\"/en-US/docs/Learn/CSS/Styling_text/Web_fonts\">Web fonts</a></li><li><a href=\"/en-US/docs/Learn/CSS/Styling_text/Typesetting_a_homepage\">Typesetting a community school homepage</a></li></ol></details></li><li class=\"toggle\"><details><summary>CSS layout</summary><ol><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout\">CSS layout</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Introduction\">Introduction to CSS layout</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Normal_Flow\">Normal Flow</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Flexbox\">Flexbox</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Grids\">Grids</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Floats\">Floats</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Positioning\">Positioning</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Multiple-column_Layout\">Multiple-column layout</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Responsive_Design\">Responsive design</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Media_queries\">Beginner's guide to media queries</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Legacy_Layout_Methods\">Legacy layout methods</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Supporting_Older_Browsers\">Supporting older browsers</a></li><li><a href=\"/en-US/docs/Learn/CSS/CSS_layout/Fundamental_Layout_Comprehension\">Fundamental layout comprehension</a></li></ol></details></li><li class=\"section\"><a href=\"/en-US/docs/Learn/JavaScript\">JavaScript — Dynamic client-side scripting</a></li><li class=\"toggle\"><details open=\"\"><summary>JavaScript first steps</summary><ol><li><a href=\"/en-US/docs/Learn/JavaScript/First_steps\">JavaScript first steps</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/What_is_JavaScript\">What is JavaScript?</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/A_first_splash\">A first splash into JavaScript</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/What_went_wrong\">What went wrong? Troubleshooting JavaScript</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Variables\">Storing the information you need — Variables</a></li><li><em><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Math\" aria-current=\"page\">Basic math in JavaScript — numbers and operators</a></em></li><li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Strings\">Handling text — strings in JavaScript</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Useful_string_methods\">Useful string methods</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Arrays\">Arrays</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/First_steps/Silly_story_generator\">Silly story generator</a></li></ol></details></li><li class=\"toggle\"><details><summary>JavaScript building blocks</summary><ol><li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks\">JavaScript building blocks</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/conditionals\">Making decisions in your code — conditionals</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code\">Looping code</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Functions\">Functions — reusable blocks of code</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Build_your_own_function\">Build your own function</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Return_values\">Function return values</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Events\">Introduction to events</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Event_bubbling\">Event bubbling</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Building_blocks/Image_gallery\">Image gallery</a></li></ol></details></li><li class=\"toggle\"><details><summary>Introducing JavaScript objects</summary><ol><li><a href=\"/en-US/docs/Learn/JavaScript/Objects\">Introducing JavaScript objects</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Basics\">JavaScript object basics</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Object_prototypes\">Object prototypes</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Object-oriented_programming\">Object-oriented programming</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Classes_in_JavaScript\">Classes in JavaScript</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Objects/JSON\">Working with JSON</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Object_building_practice\">Object building practice</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Objects/Adding_bouncing_balls_features\">Adding features to our bouncing balls demo</a></li></ol></details></li><li class=\"toggle\"><details><summary>Asynchronous JavaScript</summary><ol><li><a href=\"/en-US/docs/Learn/JavaScript/Asynchronous\">Asynchronous JavaScript</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Asynchronous/Introducing\">Introducing asynchronous JavaScript</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Asynchronous/Promises\">How to use promises</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Asynchronous/Implementing_a_promise-based_API\">How to implement a promise-based API</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Asynchronous/Introducing_workers\">Introducing workers</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Asynchronous/Sequencing_animations\">Sequencing animations</a></li></ol></details></li><li class=\"toggle\"><details><summary>Client-side web APIs</summary><ol><li><a href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs\">Client-side web APIs</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Introduction\">Introduction to web APIs</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Manipulating_documents\">Manipulating documents</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Fetching_data\">Fetching data from the server</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Third_party_APIs\">Third-party APIs</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Drawing_graphics\">Drawing graphics</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Video_and_audio_APIs\">Video and Audio APIs</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Client-side_storage\">Client-side storage</a></li></ol></details></li><li class=\"section\"><a href=\"/en-US/docs/Learn/Forms\">Web forms — Working with user data</a></li><li class=\"toggle\"><details><summary>Web form building blocks</summary><ol><li><a href=\"/en-US/docs/Learn/Forms\">Web form building blocks</a></li><li><a href=\"/en-US/docs/Learn/Forms/Your_first_form\">Your first form</a></li><li><a href=\"/en-US/docs/Learn/Forms/How_to_structure_a_web_form\">How to structure a web form</a></li><li><a href=\"/en-US/docs/Learn/Forms/Basic_native_form_controls\">Basic native form controls</a></li><li><a href=\"/en-US/docs/Learn/Forms/HTML5_input_types\">The HTML5 input types</a></li><li><a href=\"/en-US/docs/Learn/Forms/Other_form_controls\">Other form controls</a></li><li><a href=\"/en-US/docs/Learn/Forms/Styling_web_forms\">Styling web forms</a></li><li><a href=\"/en-US/docs/Learn/Forms/Advanced_form_styling\">Advanced form styling</a></li><li><a href=\"/en-US/docs/Learn/Forms/UI_pseudo-classes\">UI pseudo-classes</a></li><li><a href=\"/en-US/docs/Learn/Forms/Form_validation\">Client-side form validation</a></li><li><a href=\"/en-US/docs/Learn/Forms/Sending_and_retrieving_form_data\">Sending form data</a></li></ol></details></li><li class=\"toggle\"><details><summary>Advanced web form techniques</summary><ol><li><a href=\"/en-US/docs/Learn/Forms/How_to_build_custom_form_controls\">How to build custom form controls</a></li><li><a href=\"/en-US/docs/Learn/Forms/Sending_forms_through_JavaScript\">Sending forms through JavaScript</a></li><li><a href=\"/en-US/docs/Learn/Forms/Property_compatibility_table_for_form_controls\">CSS property compatibility table for form controls</a></li><li><a href=\"/en-US/docs/Learn/Forms/HTML_forms_in_legacy_browsers\">HTML forms in legacy browsers</a></li></ol></details></li><li class=\"section\"><a href=\"/en-US/docs/Learn/Accessibility\">Accessibility — Make the web usable by everyone</a></li><li class=\"toggle\"><details><summary>Accessibility guides</summary><ol><li><a href=\"/en-US/docs/Learn/Accessibility\">Accessibility</a></li><li><a href=\"/en-US/docs/Learn/Accessibility/What_is_accessibility\">What is accessibility?</a></li><li><a href=\"/en-US/docs/Learn/Accessibility/HTML\">HTML: A good basis for accessibility</a></li><li><a href=\"/en-US/docs/Learn/Accessibility/CSS_and_JavaScript\">CSS and JavaScript accessibility best practices</a></li><li><a href=\"/en-US/docs/Learn/Accessibility/WAI-ARIA_basics\">WAI-ARIA basics</a></li><li><a href=\"/en-US/docs/Learn/Accessibility/Multimedia\">Accessible multimedia</a></li><li><a href=\"/en-US/docs/Learn/Accessibility/Mobile\">Mobile accessibility</a></li><li><a href=\"/en-US/docs/Learn/Accessibility/Accessibility_troubleshooting\">Assessment: Accessibility troubleshooting</a></li></ol></details></li><li class=\"section\"><a href=\"/en-US/docs/Learn/Performance\">Performance — Making websites fast and responsive</a></li><li class=\"toggle\"><details><summary>Performance guides</summary><ol><li><a href=\"/en-US/docs/Learn/Performance\">Web performance</a></li><li><a href=\"/en-US/docs/Learn/Performance/why_web_performance\">The \"why\" of web performance</a></li><li><a href=\"/en-US/docs/Learn/Performance/What_is_web_performance\">What is web performance?</a></li><li><a href=\"/en-US/docs/Learn/Performance/Perceived_performance\">Perceived performance</a></li><li><a href=\"/en-US/docs/Learn/Performance/Measuring_performance\">Measuring performance</a></li><li><a href=\"/en-US/docs/Learn/Performance/Multimedia\">Multimedia: Images</a></li><li><a href=\"/en-US/docs/Learn/Performance/video\">Multimedia: video</a></li><li><a href=\"/en-US/docs/Learn/Performance/JavaScript\">JavaScript performance optimization</a></li><li><a href=\"/en-US/docs/Learn/Performance/HTML\">HTML performance optimization</a></li><li><a href=\"/en-US/docs/Learn/Performance/CSS\">CSS performance optimization</a></li><li><a href=\"/en-US/docs/Learn/Performance/business_case_for_performance\">The business case for web performance</a></li></ol></details></li><li class=\"section\"><a href=\"/en-US/docs/Learn/MathML\">MathML — Writing mathematics with MathML</a></li><li class=\"toggle\"><details><summary>MathML first steps</summary><ol><li><a href=\"/en-US/docs/Learn/MathML/First_steps\">MathML first steps</a></li><li><a href=\"/en-US/docs/Learn/MathML/First_steps/Getting_started\">Getting started with MathML</a></li><li><a href=\"/en-US/docs/Learn/MathML/First_steps/Text_containers\">MathML Text Containers</a></li><li><a href=\"/en-US/docs/Learn/MathML/First_steps/Fractions_and_roots\">MathML fractions and roots</a></li><li><a href=\"/en-US/docs/Learn/MathML/First_steps/Scripts\">MathML scripted elements</a></li><li><a href=\"/en-US/docs/Learn/MathML/First_steps/Tables\">MathML tables</a></li><li><a href=\"/en-US/docs/Learn/MathML/First_steps/Three_famous_mathematical_formulas\">Three famous mathematical formulas</a></li></ol></details></li><li class=\"section\"><a href=\"/en-US/docs/Games\">Games — Developing games for the web</a></li><li class=\"toggle\"><details><summary>Guides and tutorials</summary><ol><li><a href=\"/en-US/docs/Games/Introduction\">Introduction to game development for the Web</a></li><li><a href=\"/en-US/docs/Games/Techniques\">Techniques for game development</a></li><li><a href=\"/en-US/docs/Games/Tutorials\">Tutorials</a></li><li><a href=\"/en-US/docs/Games/Publishing_games\">Publishing games</a></li></ol></details></li><li class=\"section\"><a href=\"/en-US/docs/Learn/Tools_and_testing\">Tools and testing</a></li><li class=\"toggle\"><details><summary>Client-side web development tools</summary><ol><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools\">Understanding client-side web development tools</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Overview\">Client-side tooling overview</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Command_line\">Command line crash course</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Package_management\">Package management basics</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Introducing_complete_toolchain\">Introducing a complete toolchain</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Understanding_client-side_tools/Deployment\">Deploying our app</a></li></ol></details></li><li class=\"toggle\"><details><summary>Introduction to client-side frameworks</summary><ol><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Introduction\">Introduction to client-side frameworks</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Main_features\">Framework main features</a></li></ol></details></li><li class=\"toggle\"><details><summary>React</summary><ol><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_getting_started\">Getting started with React</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_todo_list_beginning\">Beginning our React todo list</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_components\">Componentizing our React app</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_interactivity_events_state\">React interactivity: Events and state</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_interactivity_filtering_conditional_rendering\">React interactivity: Editing, filtering, conditional rendering</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_accessibility\">Accessibility in React</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/React_resources\">React resources</a></li></ol></details></li><li class=\"toggle\"><details><summary>Ember</summary><ol><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_getting_started\">Getting started with Ember</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_structure_componentization\">Ember app structure and componentization</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_interactivity_events_state\">Ember interactivity: Events, classes and state</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_conditional_footer\">Ember Interactivity: Footer functionality, conditional rendering</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_routing\">Routing in Ember</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Ember_resources\">Ember resources and troubleshooting</a></li></ol></details></li><li class=\"toggle\"><details><summary>Vue</summary><ol><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_getting_started\">Getting started with Vue</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_first_component\">Creating our first Vue component</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_rendering_lists\">Rendering a list of Vue components</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_methods_events_models\">Adding a new todo form: Vue events, methods, and models</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_styling\">Styling Vue components with CSS</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_computed_properties\">Using Vue computed properties</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_conditional_rendering\">Vue conditional rendering: editing existing todos</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_refs_focus_management\">Vue refs and lifecycle methods for focus management</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Vue_resources\">Vue resources</a></li></ol></details></li><li class=\"toggle\"><details><summary>Svelte</summary><ol><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_getting_started\">Getting started with Svelte</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_Todo_list_beginning\">Starting our Svelte to-do list app</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_variables_props\">Dynamic behavior in Svelte: working with variables and props</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_components\">Componentizing our Svelte app</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_reactivity_lifecycle_accessibility\">Advanced Svelte: Reactivity, lifecycle, accessibility</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_stores\">Working with Svelte stores</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_TypeScript\">TypeScript support in Svelte</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Svelte_deployment_next\">Deployment and next steps</a></li></ol></details></li><li class=\"toggle\"><details><summary>Angular</summary><ol><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_getting_started\">Getting started with Angular</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_todo_list_beginning\">Beginning our Angular todo list app</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_styling\">Styling our Angular app</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_item_component\">Creating an item component</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_filtering\">Filtering our to-do items</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Client-side_JavaScript_frameworks/Angular_building\">Building Angular applications and further resources</a></li></ol></details></li><li class=\"toggle\"><details><summary>Git and GitHub</summary><ol><li><a href=\"/en-US/docs/Learn/Tools_and_testing/GitHub\">Git and GitHub</a></li></ol></details></li><li class=\"toggle\"><details><summary>Cross browser testing</summary><ol><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing\">Cross browser testing</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Introduction\">Introduction to cross-browser testing</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Testing_strategies\">Strategies for carrying out testing</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/HTML_and_CSS\">Handling common HTML and CSS problems</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/JavaScript\">Handling common JavaScript problems</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Accessibility\">Handling common accessibility problems</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Feature_detection\">Implementing feature detection</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Automated_testing\">Introduction to automated testing</a></li><li><a href=\"/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Your_own_automation_environment\">Setting up your own test automation environment</a></li></ol></details></li><li class=\"section\"><a href=\"/en-US/docs/Learn/Server-side\">Server-side website programming</a></li><li class=\"toggle\"><details><summary>First steps</summary><ol><li><a href=\"/en-US/docs/Learn/Server-side/First_steps\">Server-side website programming first steps</a></li><li><a href=\"/en-US/docs/Learn/Server-side/First_steps/Introduction\">Introduction to the server side</a></li><li><a href=\"/en-US/docs/Learn/Server-side/First_steps/Client-Server_overview\">Client-Server Overview</a></li><li><a href=\"/en-US/docs/Learn/Server-side/First_steps/Web_frameworks\">Server-side web frameworks</a></li><li><a href=\"/en-US/docs/Learn/Server-side/First_steps/Website_security\">Website security</a></li></ol></details></li><li class=\"toggle\"><details><summary>Django web framework (Python)</summary><ol><li><a href=\"/en-US/docs/Learn/Server-side/Django\">Django Web Framework (Python)</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Introduction\">Django introduction</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/development_environment\">Setting up a Django development environment</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Tutorial_local_library_website\">Django Tutorial: The Local Library website</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/skeleton_website\">Django Tutorial Part 2: Creating a skeleton website</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Models\">Django Tutorial Part 3: Using models</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Admin_site\">Django Tutorial Part 4: Django admin site</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Home_page\">Django Tutorial Part 5: Creating our home page</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Generic_views\">Django Tutorial Part 6: Generic list and detail views</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Sessions\">Django Tutorial Part 7: Sessions framework</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Authentication\">Django Tutorial Part 8: User authentication and permissions</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Forms\">Django Tutorial Part 9: Working with forms</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Testing\">Django Tutorial Part 10: Testing a Django web application</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/Deployment\">Django Tutorial Part 11: Deploying Django to production</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/web_application_security\">Django web application security</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Django/django_assessment_blog\">Assessment: DIY Django mini blog</a></li></ol></details></li><li class=\"toggle\"><details><summary>Express Web Framework (Node.js/JavaScript)</summary><ol><li><a href=\"/en-US/docs/Learn/Server-side/Express_Nodejs\">Express web framework (Node.js/JavaScript)</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/Introduction\">Express/Node introduction</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/development_environment\">Setting up a Node development environment</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/Tutorial_local_library_website\">Express Tutorial: The Local Library website</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/skeleton_website\">Express Tutorial Part 2: Creating a skeleton website</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/mongoose\">Express Tutorial Part 3: Using a Database (with Mongoose)</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/routes\">Express Tutorial Part 4: Routes and controllers</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/Displaying_data\">Express Tutorial Part 5: Displaying library data</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/forms\">Express Tutorial Part 6: Working with forms</a></li><li><a href=\"/en-US/docs/Learn/Server-side/Express_Nodejs/deployment\">Express Tutorial Part 7: Deploying to production</a></li></ol></details></li><li class=\"section\"><a href=\"/en-US/docs/Learn/Common_questions\">Further resources</a></li><li class=\"toggle\"><details><summary>Common questions</summary><ol><li><a href=\"/en-US/docs/Learn/Common_questions\">Common questions</a></li><li><a href=\"/en-US/docs/Learn/HTML/Howto\">Use HTML to solve common problems</a></li><li><a href=\"/en-US/docs/Learn/CSS/Howto\">Use CSS to solve common problems</a></li><li><a href=\"/en-US/docs/Learn/JavaScript/Howto\">Solve common problems in your JavaScript code</a></li><li><a href=\"/en-US/docs/Learn/Common_questions/Web_mechanics\">Web mechanics</a></li><li><a href=\"/en-US/docs/Learn/Common_questions/Tools_and_setup\">Tools and setup</a></li><li><a href=\"/en-US/docs/Learn/Common_questions/Design_and_accessibility\">Design and accessibility</a></li></ol></details></li></ol>","source":{"folder":"en-us/learn/javascript/first_steps/math","github_url":"https://github.com/mdn/content/blob/main/files/en-us/learn/javascript/first_steps/math/index.md","last_commit_url":"https://github.com/mdn/content/commit/93b34fcdb9cf91ff44f5dfe7f4dcd13e961962da","filename":"index.md"},"summary":"At this point in the course, we discuss math in JavaScript — how we can use operators and other features to successfully manipulate numbers to do our bidding.","title":"Basic math in JavaScript — numbers and operators","toc":[{"text":"Everybody loves math","id":"everybody_loves_math"},{"text":"Arithmetic operators","id":"arithmetic_operators"},{"text":"Increment and decrement operators","id":"increment_and_decrement_operators"},{"text":"Assignment operators","id":"assignment_operators"},{"text":"Active learning: sizing a canvas box","id":"active_learning_sizing_a_canvas_box"},{"text":"Comparison operators","id":"comparison_operators"},{"text":"Test your skills!","id":"test_your_skills!"},{"text":"Summary","id":"summary"}],"pageType":"learn-module-chapter"}}</script> <script>function gtElInit() {var lib = new google.translate.TranslateService();lib.translatePage('pl', 'fr', function () {});}</script> <script src="https://translate.google.com/translate_a/element.js?cb=gtElInit&hl=en-GB&client=wt" type="text/javascript"></script> </body> </html>