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Curso completo de Desenvolvimento Web Crie 6 projetosHTML JAVASCRIPT CSS PHP 9. JavaScript 31. Projeto final - Game estourando balões - arquivos do projeto

Curso completo de Desenvolvimento Web Crie 6 projetosHTML JAVASCRIPT CSS PHP 16. Ajax (Asynchronous Javascript and XML) 5. Requisições síncronas com links

Curso completo de Desenvolvimento Web Crie 6 projetosHTML JAVASCRIPT CSS PHP 9. JavaScript 32. Projeto final - Game estourando balões - parte 1

Curso completo de Desenvolvimento Web Crie 6 projetosHTML JAVASCRIPT CSS PHP 9. JavaScript 25. Eventos - parte 4 de 4 formulário

Curso completo de Desenvolvimento Web Crie 6 projetosHTML JAVASCRIPT CSS PHP 9. JavaScript 18. Estruturas de repetição - parte 3 de 4 do while

Curso completo de Desenvolvimento Web Crie 6 projetosHTML JAVASCRIPT CSS PHP 12. PHP 23. Estruturas de repetição - parte 3 de 5 do while

Curso completo de Desenvolvimento Web Crie 6 projetosHTML JAVASCRIPT CSS PHP 3. HTML 2. O que é HTML

Curso completo de Desenvolvimento Web Crie 6 projetosHTML JAVASCRIPT CSS PHP 17. PHP & MySQL - Projeto aplicado Twitter Clone 15. Cadastro de usuário - Bloquear inclusão de usuários já cadastrados parte 1

Curso completo de Desenvolvimento Web Crie 6 projetosHTML JAVASCRIPT CSS PHP 12. PHP 10. Download - Projeto auxiliar catálogo de produtos

Curso completo de Desenvolvimento Web Crie 6 projetosHTML JAVASCRIPT CSS PHP 9. JavaScript 14. Operadores aritméticos

Today in this all panelist episode, we talk about JS features you should avoid using. However opinions don't always align, and some come with much debate! Although we couldn't cover them all, today we discuss:eval withargumentsdo while for I++continue classesprototypesthisvar with letdeleteSponsorsTop End DevsRaygun | Click here to get started on your free 14-day trialCoaching | Top End DevsLinksJavaScript Remote Conference 2022Twitter: ?@cmaxwPicksAJ- Virginia Ctenucha Ctenucha virginica (Esper, 1794) | Butterflies and Moths of North AmericaAJ- The Mistborn Trilogy by Brandon SandersonAJ- Thread pitch gauge at Lowes.com: Search ResultsCharles- AntidoteCharles- Conferences | Top End DevsCharles- 1883 - Yellowstone Prequel (Official Site) Watch on Paramount+Dan- Can I use... Support tables for HTML5, CSS3, etcDan - War in UkraineDan- Webb Space Telescope GSFC/NASASteve- Coworker Standing At Desk Obviously Just Hasn't Learned About Chairs YetSteve - Dad Jokes

Ben finalizes Formkeep's Ember removal, toys with the idea of manual on boarding, and positions himself to begin experimenting with plans and pricing. Meanwhile, Chris deals with credit card fraud, too many inodes on Upcase's server, and finishes the changes required to offer free videos.UpcaseFormkeepBarbell Investment StrategyDesigning Forms That ConvertFree Gitsh Video from The Weekly IterationWhat is 2.5 * 26?Support Giant Robots Smashing Into Other Giant Robots

While at TXJS - Adam and Wynn caught up with Douglas Crockford, author of both JavaScript: The Good Parts and the JSON spec, and a global namespace unto himself.

Mikeal Rogers, Alex Sexton, and special guest Juan Pablo Buritica discuss all things JavaScript in Latin America. The conferences, the communities, the meetups, JavaScript tooling, and more.

Curso completo de Desenvolvimento Web Crie 6 projetosHTML JAVASCRIPT CSS PHP 9. JavaScript 4. Variáveis

Curso completo de Desenvolvimento Web Crie 6 projetosHTML JAVASCRIPT CSS PHP 5. CSS Intermediário 4. Box Model  Modelo de caixas - (Arquivos do projeto)

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30 days of JavaScript programming challenge is a step-by-step guide to learn JavaScript programming language in 30 days. This challenge may take more than 100 days, please just follow your own pace. To restore the repository download the bundle wget https://archive.org/download/github.com-Asabeneh-30-Days-Of-JavaScript_-_2022-02-09_02-39-52/Asabeneh-30-Days-Of-JavaScript_-_2022-02-09_02-39-52.bundle and run: git clone Asabeneh-30-Days-Of-JavaScript_-_2022-02-09_02-39-52.bundle Source: https://github.com/Asabeneh/30-Days-Of-JavaScript Uploader: Asabeneh Upload date: 2022-02-09

JavaScript Remote Conf 2020 May 13th to 15th - register now! Matt Crook joins the conversation to talk with the JavaScript Jabber panel to talk about his experience going through Nashville Software School. The panel discusses and asks questions about getting into programming, working through the bootcamp, and what prospects are for bootcamp graduates. Panel ? AJ O’Neal ? Aimee Knight ? Charles Max Wood ? Steve Edwards ? Dan Shappir Guest ? Matt Crook Sponsors ? Taiko ? Educative.io | Click here for 10% discount "The MaxCoders Guide to Finding Your Dream Developer Job" by Charles Max Wood is now available on Amazon. Get Your Copy Today!   Picks AJ O’Neal: ? PostgREST ? The Way of Kings ? VirtualBox ? Bootable Installers for MacOS, Windows, and more Aimee Knight: ? State of Microservices 2020 Report ? Peloton Bike Charles Max Wood: ? The Hobbit ? D&D Starter Set ? JavaScript Weekly ? Devchat.tv Remote Meetups ? Devchat.tv Remote Conferences ? Reading to Kids Steve Edwards: ? It Is Well With My Soul ? Pitbull Gold PRO Skull Shaver ? Brad Balfour Dan Shappir: ? Gödel, Escher, Bach ? Translating "The Hobbit" in Captivity Matt Crook: ? Follow Matt on Twitter > @mgcrook , Instagram , LinkedIn ? Swolenormous ? Fireship ? Static Headz ? Yugen Follow JavaScript Jabber on Twitter > @JSJabber

For Schedule of the conference, please see http://2012.gnome.asia/schedule/

Source: http://badcampuk.net/sessions/drupal-javascript-and-you-0 The limitations of a technology or platform can be best understood by examining the technologies upon which they are based - in the case of Drupal, we have already made some decisions about how it is implemented and how data is stored (PHP and a database layer such as MySQL). However, Drupal itself is extremely extensible, and Javascript offers unique opportunities for developers who are willing to get their hands dirty. This is a technical talk, starting with the basics of JQuery and integrating Javascript with Drupal, hopefully leading into discussion of options for further integration and the benefits provided.

FollowUp20 JavaScript Part13

Starter files, final projects and FAQ for my Complete JavaScript course Course Material and FAQ for my Complete JavaScript Course This repo contains starter files and the finished project files for all the projects contained in the course. Plus, I made all the course slides available for download , to make it easier to follow along the conceptual videos. 👇 Please read the following Frequently Asked Questions (FAQ) carefully before starting the course 👇 FAQ Q1: How do I download the files? A: If you're new to GitHub and just want to download the complete package, hit the green button saying "Clone or download", choose the "Download ZIP" option, and you're good to go. Q2: I'm stuck in one of the projects. Where do I get help? A: Have you extensively tried fixing the problem on your own? If you failed at fixing it, please post a detailled description of the problem to the Q&A area of that video over at Udemy , along with a codepen containing your code. You will get help as fast as possible! Please don't send me a personal message or email to fix coding problems. Q3: Brackets shows me errors, but my code works. Why is that? A: These are not errors in your code, and you can simply ignore them (they just come from so-called linters that are not correctly set up). Q4: You keep mentioning your resources page. Where can I find it? A: It's on my website at http://codingheroes.io/resources . You can subscribe for updates 😉 Q5: What Brackets and VSCode themes are you using? A: I use the theme "OS X Style | Flat & Dark" in Brackets and "Oceanic Next (dimmed bg)" in VSCode. Here is the complete setup . Q6: Can I see a final version of the course projects? A: Sure, I have an online version of all three. Here they are: Pig Game (DOM manipulation), Budgety (advanced JavaScript) and Forkify (modern JavaScript and AJAX). Q7: Videos don't load, can you fix it? A: Unfortunately, there is nothing I can do about it. The course is hosted on Udemy's platform, and sometimes they have small technical issues like this one. Please just come back a bit later or contact their support team . Q8: Videos are blurred / have low quality, can you fix it? A: Please open video settings and change the quality from 'Auto' to another value, for example 720p. If that doesn't help, please contact the Udemy support team . Q9: Are the videos downloadable? A: Yes, I made all videos downloadable on the Udemy platform so you can learn even without an internet connection. To download a video, use the settings icon in the right bottom corner of the video player. Q10: I love your courses and want to get updates on new courses. How? A: First, you can subscribe to my email list at my website . Plus, I make important announcements on twitter @jonasschmedtman , so you should definitely follow me there 🔥 Q11: How do I get my certificate of completion? A: A certificate of completion is provided by Udemy after you complete 100% of the course. After completing the course, just click on the "Your progress" indicator in the top right-hand corner of the course page. If you want to change your name on the certificate, please contact the Udemy support team . Q12: Do you accept pull requests? A: No, for the simple reason that I want this repository to contain the exact same code that is shown in the videos. However, please feel free to add an issue if you found one. To restore the repository download the bundle wget https://archive.org/download/github.com-jonasschmedtmann-complete-javascript-course_-_2019-11-17_20-33-25/jonasschmedtmann-complete-javascript-course_-_2019-11-17_20-33-25.bundle and run: git clone jonasschmedtmann-complete-javascript-course_-_2019-11-17_20-33-25.bundle Source: https://github.com/jonasschmedtmann/complete-javascript-course Uploader: jonasschmedtmann Upload date: 2019-11-17

A dump of the top

JavaScript Style Guide Airbnb JavaScript Style Guide() { A mostly reasonable approach to JavaScript Note : this guide assumes you are using Babel , and requires that you use babel-preset-airbnb or the equivalent. It also assumes you are installing shims/polyfills in your app, with airbnb-browser-shims or the equivalent. This guide is available in other languages too. See Translation Other Style Guides ES5 (Deprecated) React CSS-in-JavaScript CSS & Sass Ruby Table of Contents Types References Objects Arrays Destructuring Strings Functions Arrow Functions Classes & Constructors Modules Iterators and Generators Properties Variables Hoisting Comparison Operators & Equality Blocks Control Statements Comments Whitespace Commas Semicolons Type Casting & Coercion Naming Conventions Accessors Events jQuery ECMAScript 5 Compatibility ECMAScript 6+ (ES 2015+) Styles Standard Library Testing Performance Resources In the Wild Translation The JavaScript Style Guide Guide Chat With Us About JavaScript Contributors License Amendments Types - 1.1 Primitives : When you access a primitive type you work directly on its value. - `string`- `number`- `boolean`- `null`- `undefined`- `symbol`- `bigint````javascriptconst foo = 1;let bar = foo;bar = 9;console.log(foo, bar); // => 1, 9```- Symbols and BigInts cannot be faithfully polyfilled, so they should not be used when targeting browsers/environments that don’t support them natively. - 1.2 Complex : When you access a complex type you work on a reference to its value. - `object`- `array`- `function````javascriptconst foo = [1, 2];const bar = foo;bar[0] = 9;console.log(foo[0], bar[0]); // => 9, 9``` ⬆ back to top References - 2.1 Use const for all of your references; avoid using var . eslint: <code>prefer-const</code> , <code>no-const-assign</code> > Why? This ensures that you can’t reassign your references, which can lead to bugs and difficult to comprehend code.```javascript// badvar a = 1;var b = 2;// goodconst a = 1;const b = 2;``` - 2.2 If you must reassign references, use let instead of var . eslint: <code>no-var</code> > Why? `let` is block-scoped rather than function-scoped like `var`.```javascript// badvar count = 1;if (true) { count += 1;}// good, use the let.let count = 1;if (true) { count += 1;}``` - 2.3 Note that both let and const are block-scoped, whereas var is function-scoped. ```javascript// const and let only exist in the blocks they are defined in.{ let a = 1; const b = 1; var c = 1;}console.log(a); // ReferenceErrorconsole.log(b); // ReferenceErrorconsole.log(c); // Prints 1```In the above code, you can see that referencing `a` and `b` will produce a ReferenceError, while `c` contains the number. This is because `a` and `b` are block scoped, while `c` is scoped to the containing function. ⬆ back to top Objects - 3.1 Use the literal syntax for object creation. eslint: <code>no-new-object</code> ```javascript// badconst item = new Object();// goodconst item = {};``` - 3.2 Use computed property names when creating objects with dynamic property names. > Why? They allow you to define all the properties of an object in one place.```javascriptfunction getKey(k) { return `a key named ${k}`;}// badconst obj = { id: 5, name: 'San Francisco',};obj[getKey('enabled')] = true;// goodconst obj = { id: 5, name: 'San Francisco', [getKey('enabled')]: true,};``` - 3.3 Use object method shorthand. eslint: <code>object-shorthand</code> ```javascript// badconst atom = { value: 1, addValue: function (value) { return atom.value + value; },};// goodconst atom = { value: 1, addValue(value) { return atom.value + value; },};``` - 3.4 Use property value shorthand. eslint: <code>object-shorthand</code> > Why? It is shorter and descriptive.```javascriptconst lukeSkywalker = 'Luke Skywalker';// badconst obj = { lukeSkywalker: lukeSkywalker,};// goodconst obj = { lukeSkywalker,};``` - 3.5 Group your shorthand properties at the beginning of your object declaration. > Why? It’s easier to tell which properties are using the shorthand.```javascriptconst anakinSkywalker = 'Anakin Skywalker';const lukeSkywalker = 'Luke Skywalker';// badconst obj = { episodeOne: 1, twoJediWalkIntoACantina: 2, lukeSkywalker, episodeThree: 3, mayTheFourth: 4, anakinSkywalker,};// goodconst obj = { lukeSkywalker, anakinSkywalker, episodeOne: 1, twoJediWalkIntoACantina: 2, episodeThree: 3, mayTheFourth: 4,};``` - 3.6 Only quote properties that are invalid identifiers. eslint: <code>quote-props</code> > Why? In general we consider it subjectively easier to read. It improves syntax highlighting, and is also more easily optimized by many JS engines.```javascript// badconst bad = { 'foo': 3, 'bar': 4, 'data-blah': 5,};// goodconst good = { foo: 3, bar: 4, 'data-blah': 5,};``` - 3.7 Do not call Object.prototype methods directly, such as hasOwnProperty , propertyIsEnumerable , and isPrototypeOf . eslint: <code>no-prototype-builtins</code> > Why? These methods may be shadowed by properties on the object in question - consider `{ hasOwnProperty: false }` - or, the object may be a null object (`Object.create(null)`).```javascript// badconsole.log(object.hasOwnProperty(key));// goodconsole.log(Object.prototype.hasOwnProperty.call(object, key));// bestconst has = Object.prototype.hasOwnProperty; // cache the lookup once, in module scope.console.log(has.call(object, key));/* or */import has from 'has'; // https://www.npmjs.com/package/hasconsole.log(has(object, key));``` - 3.8 Prefer the object spread syntax over <code>Object.assign</code> to shallow-copy objects. Use the object rest parameter syntax to get a new object with certain properties omitted. eslint: <code>prefer-object-spread</code> ```javascript// very badconst original = { a: 1, b: 2 };const copy = Object.assign(original, { c: 3 }); // this mutates `original` ಠ_ಠdelete copy.a; // so does this// badconst original = { a: 1, b: 2 };const copy = Object.assign({}, original, { c: 3 }); // copy => { a: 1, b: 2, c: 3 }// goodconst original = { a: 1, b: 2 };const copy = { ...original, c: 3 }; // copy => { a: 1, b: 2, c: 3 }const { a, ...noA } = copy; // noA => { b: 2, c: 3 }``` ⬆ back to top Arrays - 4.1 Use the literal syntax for array creation. eslint: <code>no-array-constructor</code> ```javascript// badconst items = new Array();// goodconst items = [];``` - 4.2 Use Array#push instead of direct assignment to add items to an array. ```javascriptconst someStack = [];// badsomeStack[someStack.length] = 'abracadabra';// goodsomeStack.push('abracadabra');``` - 4.3 Use array spreads ... to copy arrays. ```javascript// badconst len = items.length;const itemsCopy = [];let i;for (i = 0; i < len; i += 1) { itemsCopy[i] = items[i];}// goodconst itemsCopy = [...items];``` - 4.4 To convert an iterable object to an array, use spreads ... instead of <code>Array.from</code> ```javascriptconst foo = document.querySelectorAll('.foo');// goodconst nodes = Array.from(foo);// bestconst nodes = [...foo];``` - 4.5 Use <code>Array.from</code> for converting an array-like object to an array. ```javascriptconst arrLike = { 0: 'foo', 1: 'bar', 2: 'baz', length: 3 };// badconst arr = Array.prototype.slice.call(arrLike);// goodconst arr = Array.from(arrLike);``` - 4.6 Use <code>Array.from</code> instead of spread ... for mapping over iterables, because it avoids creating an intermediate array. ```javascript// badconst baz = [...foo].map(bar);// goodconst baz = Array.from(foo, bar);``` - 4.7 Use return statements in array method callbacks. It’s ok to omit the return if the function body consists of a single statement returning an expression without side effects, following 8.2 . eslint: <code>array-callback-return</code> ```javascript// good[1, 2, 3].map((x) => { const y = x + 1; return x * y;});// good[1, 2, 3].map((x) => x + 1);// bad - no returned value means `acc` becomes undefined after the first iteration[[0, 1], [2, 3], [4, 5]].reduce((acc, item, index) => { const flatten = acc.concat(item);});// good[[0, 1], [2, 3], [4, 5]].reduce((acc, item, index) => { const flatten = acc.concat(item); return flatten;});// badinbox.filter((msg) => { const { subject, author } = msg; if (subject === 'Mockingbird') { return author === 'Harper Lee'; } else { return false; }});// goodinbox.filter((msg) => { const { subject, author } = msg; if (subject === 'Mockingbird') { return author === 'Harper Lee'; } return false;});``` - 4.8 Use line breaks after open and before close array brackets if an array has multiple lines ```javascript// badconst arr = [ [0, 1], [2, 3], [4, 5],];const objectInArray = [{ id: 1,}, { id: 2,}];const numberInArray = [ 1, 2,];// goodconst arr = [[0, 1], [2, 3], [4, 5]];const objectInArray = [ { id: 1, }, { id: 2, },];const numberInArray = [ 1, 2,];``` ⬆ back to top Destructuring - 5.1 Use object destructuring when accessing and using multiple properties of an object. eslint: <code>prefer-destructuring</code> > Why? Destructuring saves you from creating temporary references for those properties, and from repetitive access of the object. Repeating object access creates more repetitive code, requires more reading, and creates more opportunities for mistakes. Destructuring objects also provides a single site of definition of the object structure that is used in the block, rather than requiring reading the entire block to determine what is used.```javascript// badfunction getFullName(user) { const firstName = user.firstName; const lastName = user.lastName; return `${firstName} ${lastName}`;}// goodfunction getFullName(user) { const { firstName, lastName } = user; return `${firstName} ${lastName}`;}// bestfunction getFullName({ firstName, lastName }) { return `${firstName} ${lastName}`;}``` - 5.2 Use array destructuring. eslint: <code>prefer-destructuring</code> ```javascriptconst arr = [1, 2, 3, 4];// badconst first = arr[0];const second = arr[1];// goodconst [first, second] = arr;``` - 5.3 Use object destructuring for multiple return values, not array destructuring. > Why? You can add new properties over time or change the order of things without breaking call sites.```javascript// badfunction processInput(input) { // then a miracle occurs return [left, right, top, bottom];}// the caller needs to think about the order of return dataconst [left, __, top] = processInput(input);// goodfunction processInput(input) { // then a miracle occurs return { left, right, top, bottom };}// the caller selects only the data they needconst { left, top } = processInput(input);``` ⬆ back to top Strings - 6.1 Use single quotes '' for strings. eslint: <code>quotes</code> ```javascript// badconst name = "Capt. Janeway";// bad - template literals should contain interpolation or newlinesconst name = `Capt. Janeway`;// goodconst name = 'Capt. Janeway';``` - 6.2 Strings that cause the line to go over 100 characters should not be written across multiple lines using string concatenation. > Why? Broken strings are painful to work with and make code less searchable.```javascript// badconst errorMessage = 'This is a super long error that was thrown because \of Batman. When you stop to think about how Batman had anything to do \with this, you would get nowhere \fast.';// badconst errorMessage = 'This is a super long error that was thrown because ' + 'of Batman. When you stop to think about how Batman had anything to do ' + 'with this, you would get nowhere fast.';// goodconst errorMessage = 'This is a super long error that was thrown because of Batman. When you stop to think about how Batman had anything to do with this, you would get nowhere fast.';``` - 6.3 When programmatically building up strings, use template strings instead of concatenation. eslint: <code>prefer-template</code> <code>template-curly-spacing</code> > Why? Template strings give you a readable, concise syntax with proper newlines and string interpolation features.```javascript// badfunction sayHi(name) { return 'How are you, ' + name + '?';}// badfunction sayHi(name) { return ['How are you, ', name, '?'].join();}// badfunction sayHi(name) { return `How are you, ${ name }?`;}// goodfunction sayHi(name) { return `How are you, ${name}?`;}``` - 6.4 Never use eval() on a string, it opens too many vulnerabilities. eslint: <code>no-eval</code> - 6.5 Do not unnecessarily escape characters in strings. eslint: <code>no-useless-escape</code> > Why? Backslashes harm readability, thus they should only be present when necessary.```javascript// badconst foo = '\'this\' \i\s \"quoted\"';// goodconst foo = '\'this\' is "quoted"';const foo = `my name is '${name}'`;``` ⬆ back to top Functions - 7.1 Use named function expressions instead of function declarations. eslint: <code>func-style</code> > Why? Function declarations are hoisted, which means that it’s easy - too easy - to reference the function before it is defined in the file. This harms readability and maintainability. If you find that a function’s definition is large or complex enough that it is interfering with understanding the rest of the file, then perhaps it’s time to extract it to its own module! Don’t forget to explicitly name the expression, regardless of whether or not the name is inferred from the containing variable (which is often the case in modern browsers or when using compilers such as Babel). This eliminates any assumptions made about the Error’s call stack. ([Discussion](https://github.com/airbnb/javascript/issues/794))```javascript// badfunction foo() { // ...}// badconst foo = function () { // ...};// good// lexical name distinguished from the variable-referenced invocation(s)const short = function longUniqueMoreDescriptiveLexicalFoo() { // ...};``` - 7.2 Wrap immediately invoked function expressions in parentheses. eslint: <code>wrap-iife</code> > Why? An immediately invoked function expression is a single unit - wrapping both it, and its invocation parens, in parens, cleanly expresses this. Note that in a world with modules everywhere, you almost never need an IIFE.```javascript// immediately-invoked function expression (IIFE)(function () { console.log('Welcome to the Internet. Please follow me.');}());``` - 7.3 Never declare a function in a non-function block ( if , while , etc). Assign the function to a variable instead. Browsers will allow you to do it, but they all interpret it differently, which is bad news bears. eslint: <code>no-loop-func</code> - 7.4 Note: ECMA-262 defines a block as a list of statements. A function declaration is not a statement. ```javascript// badif (currentUser) { function test() { console.log('Nope.'); }}// goodlet test;if (currentUser) { test = () => { console.log('Yup.'); };}``` - 7.5 Never name a parameter arguments . This will take precedence over the arguments object that is given to every function scope. ```javascript// badfunction foo(name, options, arguments) { // ...}// goodfunction foo(name, options, args) { // ...}``` - 7.6 Never use arguments , opt to use rest syntax ... instead. eslint: <code>prefer-rest-params</code> > Why? `...` is explicit about which arguments you want pulled. Plus, rest arguments are a real Array, and not merely Array-like like `arguments`.```javascript// badfunction concatenateAll() { const args = Array.prototype.slice.call(arguments); return args.join('');}// goodfunction concatenateAll(...args) { return args.join('');}``` - 7.7 Use default parameter syntax rather than mutating function arguments. ```javascript// really badfunction handleThings(opts) { // No! We shouldn’t mutate function arguments. // Double bad: if opts is falsy it'll be set to an object which may // be what you want but it can introduce subtle bugs. opts = opts || {}; // ...}// still badfunction handleThings(opts) { if (opts === void 0) { opts = {}; } // ...}// goodfunction handleThings(opts = {}) { // ...}``` - 7.8 Avoid side effects with default parameters. > Why? They are confusing to reason about.```javascriptvar b = 1;// badfunction count(a = b++) { console.log(a);}count(); // 1count(); // 2count(3); // 3count(); // 3``` - 7.9 Always put default parameters last. eslint: <code>default-param-last</code> ```javascript// badfunction handleThings(opts = {}, name) { // ...}// goodfunction handleThings(name, opts = {}) { // ...}``` - 7.10 Never use the Function constructor to create a new function. eslint: <code>no-new-func</code> > Why? Creating a function in this way evaluates a string similarly to `eval()`, which opens vulnerabilities.```javascript// badvar add = new Function('a', 'b', 'return a + b');// still badvar subtract = Function('a', 'b', 'return a - b');``` - 7.11 Spacing in a function signature. eslint: <code>space-before-function-paren</code> <code>space-before-blocks</code> > Why? Consistency is good, and you shouldn’t have to add or remove a space when adding or removing a name.```javascript// badconst f = function(){};const g = function (){};const h = function() {};// goodconst x = function () {};const y = function a() {};``` - 7.12 Never mutate parameters. eslint: <code>no-param-reassign</code> > Why? Manipulating objects passed in as parameters can cause unwanted variable side effects in the original caller.```javascript// badfunction f1(obj) { obj.key = 1;}// goodfunction f2(obj) { const key = Object.prototype.hasOwnProperty.call(obj, 'key') ? obj.key : 1;}``` - 7.13 Never reassign parameters. eslint: <code>no-param-reassign</code> > Why? Reassigning parameters can lead to unexpected behavior, especially when accessing the `arguments` object. It can also cause optimization issues, especially in V8.```javascript// badfunction f1(a) { a = 1; // ...}function f2(a) { if (!a) { a = 1; } // ...}// goodfunction f3(a) { const b = a || 1; // ...}function f4(a = 1) { // ...}``` - 7.14 Prefer the use of the spread syntax ... to call variadic functions. eslint: <code>prefer-spread</code> > Why? It’s cleaner, you don’t need to supply a context, and you can not easily compose `new` with `apply`.```javascript// badconst x = [1, 2, 3, 4, 5];console.log.apply(console, x);// goodconst x = [1, 2, 3, 4, 5];console.log(...x);// badnew (Function.prototype.bind.apply(Date, [null, 2016, 8, 5]));// goodnew Date(...[2016, 8, 5]);``` - 7.15 Functions with multiline signatures, or invocations, should be indented just like every other multiline list in this guide: with each item on a line by itself, with a trailing comma on the last item. eslint: <code>function-paren-newline</code> ```javascript// badfunction foo(bar, baz, quux) { // ...}// goodfunction foo( bar, baz, quux,) { // ...}// badconsole.log(foo, bar, baz);// goodconsole.log( foo, bar, baz,);``` ⬆ back to top Arrow Functions - 8.1 When you must use an anonymous function (as when passing an inline callback), use arrow function notation. eslint: <code>prefer-arrow-callback</code> , <code>arrow-spacing</code> > Why? It creates a version of the function that executes in the context of `this`, which is usually what you want, and is a more concise syntax.> Why not? If you have a fairly complicated function, you might move that logic out into its own named function expression.```javascript// bad[1, 2, 3].map(function (x) { const y = x + 1; return x * y;});// good[1, 2, 3].map((x) => { const y = x + 1; return x * y;});``` - 8.2 If the function body consists of a single statement returning an expression without side effects, omit the braces and use the implicit return. Otherwise, keep the braces and use a return statement. eslint: <code>arrow-parens</code> , <code>arrow-body-style</code> > Why? Syntactic sugar. It reads well when multiple functions are chained together.```javascript// bad[1, 2, 3].map((number) => { const nextNumber = number + 1; `A string containing the ${nextNumber}.`;});// good[1, 2, 3].map((number) => `A string containing the ${number + 1}.`);// good[1, 2, 3].map((number) => { const nextNumber = number + 1; return `A string containing the ${nextNumber}.`;});// good[1, 2, 3].map((number, index) => ({ [index]: number,}));// No implicit return with side effectsfunction foo(callback) { const val = callback(); if (val === true) { // Do something if callback returns true }}let bool = false;// badfoo(() => bool = true);// goodfoo(() => { bool = true;});``` - 8.3 In case the expression spans over multiple lines, wrap it in parentheses for better readability. > Why? It shows clearly where the function starts and ends.```javascript// bad['get', 'post', 'put'].map((httpMethod) => Object.prototype.hasOwnProperty.call( httpMagicObjectWithAVeryLongName, httpMethod, ));// good['get', 'post', 'put'].map((httpMethod) => ( Object.prototype.hasOwnProperty.call( httpMagicObjectWithAVeryLongName, httpMethod, )));``` - 8.4 Always include parentheses around arguments for clarity and consistency. eslint: <code>arrow-parens</code> > Why? Minimizes diff churn when adding or removing arguments.```javascript// bad[1, 2, 3].map(x => x * x);// good[1, 2, 3].map((x) => x * x);// bad[1, 2, 3].map(number => ( `A long string with the ${number}. It’s so long that we don’t want it to take up space on the .map line!`));// good[1, 2, 3].map((number) => ( `A long string with the ${number}. It’s so long that we don’t want it to take up space on the .map line!`));// bad[1, 2, 3].map(x => { const y = x + 1; return x * y;});// good[1, 2, 3].map((x) => { const y = x + 1; return x * y;});``` - 8.5 Avoid confusing arrow function syntax ( => ) with comparison operators ( <= , >= ). eslint: <code>no-confusing-arrow</code> ```javascript// badconst itemHeight = (item) => item.height <= 256 ? item.largeSize : item.smallSize;// badconst itemHeight = (item) => item.height >= 256 ? item.largeSize : item.smallSize;// goodconst itemHeight = (item) => (item.height <= 256 ? item.largeSize : item.smallSize);// goodconst itemHeight = (item) => { const { height, largeSize, smallSize } = item; return height <= 256 ? largeSize : smallSize;};``` - 8.6 Enforce the location of arrow function bodies with implicit returns. eslint: <code>implicit-arrow-linebreak</code> ```javascript// bad(foo) => bar;(foo) => (bar);// good(foo) => bar;(foo) => (bar);(foo) => ( bar)``` ⬆ back to top Classes & Constructors - 9.1 Always use class . Avoid manipulating prototype directly. > Why? `class` syntax is more concise and easier to reason about.```javascript// badfunction Queue(contents = []) { this.queue = [...contents];}Queue.prototype.pop = function () { const value = this.queue[0]; this.queue.splice(0, 1); return value;};// goodclass Queue { constructor(contents = []) { this.queue = [...contents]; } pop() { const value = this.queue[0]; this.queue.splice(0, 1); return value; }}``` - 9.2 Use extends for inheritance. > Why? It is a built-in way to inherit prototype functionality without breaking `instanceof`.```javascript// badconst inherits = require('inherits');function PeekableQueue(contents) { Queue.apply(this, contents);}inherits(PeekableQueue, Queue);PeekableQueue.prototype.peek = function () { return this.queue[0];};// goodclass PeekableQueue extends Queue { peek() { return this.queue[0]; }}``` - 9.3 Methods can return this to help with method chaining. ```javascript// badJedi.prototype.jump = function () { this.jumping = true; return true;};Jedi.prototype.setHeight = function (height) { this.height = height;};const luke = new Jedi();luke.jump(); // => trueluke.setHeight(20); // => undefined// goodclass Jedi { jump() { this.jumping = true; return this; } setHeight(height) { this.height = height; return this; }}const luke = new Jedi();luke.jump() .setHeight(20);``` - 9.4 It’s okay to write a custom toString() method, just make sure it works successfully and causes no side effects. ```javascriptclass Jedi { constructor(options = {}) { this.name = options.name || 'no name'; } getName() { return this.name; } toString() { return `Jedi - ${this.getName()}`; }}``` - 9.5 Classes have a default constructor if one is not specified. An empty constructor function or one that just delegates to a parent class is unnecessary. eslint: <code>no-useless-constructor</code> ```javascript// badclass Jedi { constructor() {} getName() { return this.name; }}// badclass Rey extends Jedi { constructor(...args) { super(...args); }}// goodclass Rey extends Jedi { constructor(...args) { super(...args); this.name = 'Rey'; }}``` - 9.6 Avoid duplicate class members. eslint: <code>no-dupe-class-members</code> > Why? Duplicate class member declarations will silently prefer the last one - having duplicates is almost certainly a bug.```javascript// badclass Foo { bar() { return 1; } bar() { return 2; }}// goodclass Foo { bar() { return 1; }}// goodclass Foo { bar() { return 2; }}``` - 9.7 Class methods should use this or be made into a static method unless an external library or framework requires using specific non-static methods. Being an instance method should indicate that it behaves differently based on properties of the receiver. eslint: <code>class-methods-use-this</code> ```javascript// badclass Foo { bar() { console.log('bar'); }}// good - this is usedclass Foo { bar() { console.log(this.bar); }}// good - constructor is exemptclass Foo { constructor() { // ... }}// good - static methods aren't expected to use thisclass Foo { static bar() { console.log('bar'); }}``` ⬆ back to top Modules - 10.1 Always use modules ( import / export ) over a non-standard module system. You can always transpile to your preferred module system. > Why? Modules are the future, let’s start using the future now.```javascript// badconst AirbnbStyleGuide = require('./AirbnbStyleGuide');module.exports = AirbnbStyleGuide.es6;// okimport AirbnbStyleGuide from './AirbnbStyleGuide';export default AirbnbStyleGuide.es6;// bestimport { es6 } from './AirbnbStyleGuide';export default es6;``` - 10.2 Do not use wildcard imports. > Why? This makes sure you have a single default export.```javascript// badimport * as AirbnbStyleGuide from './AirbnbStyleGuide';// goodimport AirbnbStyleGuide from './AirbnbStyleGuide';``` - 10.3 And do not export directly from an import. > Why? Although the one-liner is concise, having one clear way to import and one clear way to export makes things consistent.```javascript// bad// filename es6.jsexport { es6 as default } from './AirbnbStyleGuide';// good// filename es6.jsimport { es6 } from './AirbnbStyleGuide';export default es6;``` - 10.4 Only import from a path in one place. eslint: <code>no-duplicate-imports</code> Why? Having multiple lines that import from the same path can make code harder to maintain. ```javascript// badimport foo from 'foo';// … some other imports … //import { named1, named2 } from 'foo';// goodimport foo, { named1, named2 } from 'foo';// goodimport foo, { named1, named2,} from 'foo';``` - 10.5 Do not export mutable bindings. eslint: <code>import/no-mutable-exports</code> Why? Mutation should be avoided in general, but in particular when exporting mutable bindings. While this technique may be needed for some special cases, in general, only constant references should be exported. ```javascript// badlet foo = 3;export { foo };// goodconst foo = 3;export { foo };``` - 10.6 In modules with a single export, prefer default export over named export. eslint: <code>import/prefer-default-export</code> Why? To encourage more files that only ever export one thing, which is better for readability and maintainability. ```javascript// badexport function foo() {}// goodexport default function foo() {}``` - 10.7 Put all import s above non-import statements. eslint: <code>import/first</code> Why? Since import s are hoisted, keeping them all at the top prevents surprising behavior. ```javascript// badimport foo from 'foo';foo.init();import bar from 'bar';// goodimport foo from 'foo';import bar from 'bar';foo.init();``` - 10.8 Multiline imports should be indented just like multiline array and object literals. eslint: <code>object-curly-newline</code> > Why? The curly braces follow the same indentation rules as every other curly brace block in the style guide, as do the trailing commas.```javascript// badimport {longNameA, longNameB, longNameC, longNameD, longNameE} from 'path';// goodimport { longNameA, longNameB, longNameC, longNameD, longNameE,} from 'path';``` - 10.9 Disallow Webpack loader syntax in module import statements. eslint: <code>import/no-webpack-loader-syntax</code> Why? Since using Webpack syntax in the imports couples the code to a module bundler. Prefer using the loader syntax in webpack.config.js . ```javascript// badimport fooSass from 'css!sass!foo.scss';import barCss from 'style!css!bar.css';// goodimport fooSass from 'foo.scss';import barCss from 'bar.css';``` - 10.10 Do not include JavaScript filename extensions eslint: <code>import/extensions</code> Why? Including extensions inhibits refactoring, and inappropriately hardcodes implementation details of the module you're importing in every consumer. ```javascript// badimport foo from './foo.js';import bar from './bar.jsx';import baz from './baz/index.jsx';// goodimport foo from './foo';import bar from './bar';import baz from './baz';``` ⬆ back to top Iterators and Generators - 11.1 Don’t use iterators. Prefer JavaScript’s higher-order functions instead of loops like for-in or for-of . eslint: <code>no-iterator</code> <code>no-restricted-syntax</code> > Why? This enforces our immutable rule. Dealing with pure functions that return values is easier to reason about than side effects.> Use `map()` / `every()` / `filter()` / `find()` / `findIndex()` / `reduce()` / `some()` / ... to iterate over arrays, and `Object.keys()` / `Object.values()` / `Object.entries()` to produce arrays so you can iterate over objects.```javascriptconst numbers = [1, 2, 3, 4, 5];// badlet sum = 0;for (let num of numbers) { sum += num;}sum === 15;// goodlet sum = 0;numbers.forEach((num) => { sum += num;});sum === 15;// best (use the functional force)const sum = numbers.reduce((total, num) => total + num, 0);sum === 15;// badconst increasedByOne = [];for (let i = 0; i < numbers.length; i++) { increasedByOne.push(numbers[i] + 1);}// goodconst increasedByOne = [];numbers.forEach((num) => { increasedByOne.push(num + 1);});// best (keeping it functional)const increasedByOne = numbers.map((num) => num + 1);``` - 11.2 Don’t use generators for now. > Why? They don’t transpile well to ES5. - 11.3 If you must use generators, or if you disregard our advice , make sure their function signature is spaced properly. eslint: <code>generator-star-spacing</code> > Why? `function` and `*` are part of the same conceptual keyword - `*` is not a modifier for `function`, `function*` is a unique construct, different from `function`.```javascript// badfunction * foo() { // ...}// badconst bar = function * () { // ...};// badconst baz = function *() { // ...};// badconst quux = function*() { // ...};// badfunction*foo() { // ...}// badfunction *foo() { // ...}// very badfunction*foo() { // ...}// very badconst wat = function*() { // ...};// goodfunction* foo() { // ...}// goodconst foo = function* () { // ...};``` ⬆ back to top Properties - 12.1 Use dot notation when accessing properties. eslint: <code>dot-notation</code> ```javascriptconst luke = { jedi: true, age: 28,};// badconst isJedi = luke['jedi'];// goodconst isJedi = luke.jedi;``` - 12.2 Use bracket notation [] when accessing properties with a variable. ```javascriptconst luke = { jedi: true, age: 28,};function getProp(prop) { return luke[prop];}const isJedi = getProp('jedi');``` - 12.3 Use exponentiation operator ** when calculating exponentiations. eslint: <code>no-restricted-properties</code> . ```javascript// badconst binary = Math.pow(2, 10);// goodconst binary = 2 ** 10;``` ⬆ back to top Variables - 13.1 Always use const or let to declare variables. Not doing so will result in global variables. We want to avoid polluting the global namespace. Captain Planet warned us of that. eslint: <code>no-undef</code> <code>prefer-const</code> ```javascript// badsuperPower = new SuperPower();// goodconst superPower = new SuperPower();``` - 13.2 Use one const or let declaration per variable or assignment. eslint: <code>one-var</code> > Why? It’s easier to add new variable declarations this way, and you never have to worry about swapping out a `;` for a `,` or introducing punctuation-only diffs. You can also step through each declaration with the debugger, instead of jumping through all of them at once.```javascript// badconst items = getItems(), goSportsTeam = true, dragonball = 'z';// bad// (compare to above, and try to spot the mistake)const items = getItems(), goSportsTeam = true; dragonball = 'z';// goodconst items = getItems();const goSportsTeam = true;const dragonball = 'z';``` - 13.3 Group all your const s and then group all your let s. > Why? This is helpful when later on you might need to assign a variable depending on one of the previously assigned variables.```javascript// badlet i, len, dragonball, items = getItems(), goSportsTeam = true;// badlet i;const items = getItems();let dragonball;const goSportsTeam = true;let len;// goodconst goSportsTeam = true;const items = getItems();let dragonball;let i;let length;``` - 13.4 Assign variables where you need them, but place them in a reasonable place. > Why? `let` and `const` are block scoped and not function scoped.```javascript// bad - unnecessary function callfunction checkName(hasName) { const name = getName(); if (hasName === 'test') { return false; } if (name === 'test') { this.setName(''); return false; } return name;}// goodfunction checkName(hasName) { if (hasName === 'test') { return false; } const name = getName(); if (name === 'test') { this.setName(''); return false; } return name;}``` - 13.5 Don’t chain variable assignments. eslint: <code>no-multi-assign</code> > Why? Chaining variable assignments creates implicit global variables.```javascript// bad(function example() { // JavaScript interprets this as // let a = ( b = ( c = 1 ) ); // The let keyword only applies to variable a; variables b and c become // global variables. let a = b = c = 1;}());console.log(a); // throws ReferenceErrorconsole.log(b); // 1console.log(c); // 1// good(function example() { let a = 1; let b = a; let c = a;}());console.log(a); // throws ReferenceErrorconsole.log(b); // throws ReferenceErrorconsole.log(c); // throws ReferenceError// the same applies for `const```` - 13.6 Avoid using unary increments and decrements ( ++ , -- ). eslint <code>no-plusplus</code> > Why? Per the eslint documentation, unary increment and decrement statements are subject to automatic semicolon insertion and can cause silent errors with incrementing or decrementing values within an application. It is also more expressive to mutate your values with statements like `num += 1` instead of `num++` or `num ++`. Disallowing unary increment and decrement statements also prevents you from pre-incrementing/pre-decrementing values unintentionally which can also cause unexpected behavior in your programs.```javascript// badconst array = [1, 2, 3];let num = 1;num++;--num;let sum = 0;let truthyCount = 0;for (let i = 0; i < array.length; i++) { let value = array[i]; sum += value; if (value) { truthyCount++; }}// goodconst array = [1, 2, 3];let num = 1;num += 1;num -= 1;const sum = array.reduce((a, b) => a + b, 0);const truthyCount = array.filter(Boolean).length;``` - 13.7 Avoid linebreaks before or after = in an assignment. If your assignment violates <code>max-len</code> , surround the value in parens. eslint <code>operator-linebreak</code> . > Why? Linebreaks surrounding `=` can obfuscate the value of an assignment.```javascript// badconst foo = superLongLongLongLongLongLongLongLongFunctionName();// badconst foo = 'superLongLongLongLongLongLongLongLongString';// goodconst foo = ( superLongLongLongLongLongLongLongLongFunctionName());// goodconst foo = 'superLongLongLongLongLongLongLongLongString';``` - 13.8 Disallow unused variables. eslint: <code>no-unused-vars</code> > Why? Variables that are declared and not used anywhere in the code are most likely an error due to incomplete refactoring. Such variables take up space in the code and can lead to confusion by readers.```javascript// badvar some_unused_var = 42;// Write-only variables are not considered as used.var y = 10;y = 5;// A read for a modification of itself is not considered as used.var z = 0;z = z + 1;// Unused function arguments.function getX(x, y) { return x;}// goodfunction getXPlusY(x, y) { return x + y;}var x = 1;var y = a + 2;alert(getXPlusY(x, y));// 'type' is ignored even if unused because it has a rest property sibling.// This is a form of extracting an object that omits the specified keys.var { type, ...coords } = data;// 'coords' is now the 'data' object without its 'type' property.``` ⬆ back to top Hoisting - 14.1 var declarations get hoisted to the top of their closest enclosing function scope, their assignment does not. const and let declarations are blessed with a new concept called Temporal Dead Zones (TDZ) . It’s important to know why typeof is no longer safe . ```javascript// we know this wouldn’t work (assuming there// is no notDefined global variable)function example() { console.log(notDefined); // => throws a ReferenceError}// creating a variable declaration after you// reference the variable will work due to// variable hoisting. Note: the assignment// value of `true` is not hoisted.function example() { console.log(declaredButNotAssigned); // => undefined var declaredButNotAssigned = true;}// the interpreter is hoisting the variable// declaration to the top of the scope,// which means our example could be rewritten as:function example() { let declaredButNotAssigned; console.log(declaredButNotAssigned); // => undefined declaredButNotAssigned = true;}// using const and letfunction example() { console.log(declaredButNotAssigned); // => throws a ReferenceError console.log(typeof declaredButNotAssigned); // => throws a ReferenceError const declaredButNotAssigned = true;}``` - 14.2 Anonymous function expressions hoist their variable name, but not the function assignment. ```javascriptfunction example() { console.log(anonymous); // => undefined anonymous(); // => TypeError anonymous is not a function var anonymous = function () { console.log('anonymous function expression'); };}``` - 14.3 Named function expressions hoist the variable name, not the function name or the function body. ```javascriptfunction example() { console.log(named); // => undefined named(); // => TypeError named is not a function superPower(); // => ReferenceError superPower is not defined var named = function superPower() { console.log('Flying'); };}// the same is true when the function name// is the same as the variable name.function example() { console.log(named); // => undefined named(); // => TypeError named is not a function var named = function named() { console.log('named'); };}``` - 14.4 Function declarations hoist their name and the function body. ```javascriptfunction example() { superPower(); // => Flying function superPower() { console.log('Flying'); }}``` For more information refer to JavaScript Scoping & Hoisting by Ben Cherry . ⬆ back to top Comparison Operators & Equality - 15.1 Use === and !== over == and != . eslint: <code>eqeqeq</code> - 15.2 Conditional statements such as the if statement evaluate their expression using coercion with the ToBoolean abstract method and always follow these simple rules: - **Objects** evaluate to **true**- **Undefined** evaluates to **false**- **Null** evaluates to **false**- **Booleans** evaluate to **the value of the boolean**- **Numbers** evaluate to **false** if **+0, -0, or NaN**, otherwise **true**- **Strings** evaluate to **false** if an empty string `''`, otherwise **true**```javascriptif ([0] && []) { // true // an array (even an empty one) is an object, objects will evaluate to true}``` - 15.3 Use shortcuts for booleans, but explicit comparisons for strings and numbers. ```javascript// badif (isValid === true) { // ...}// goodif (isValid) { // ...}// badif (name) { // ...}// goodif (name !== '') { // ...}// badif (collection.length) { // ...}// goodif (collection.length > 0) { // ...}``` - 15.4 For more information see Truth Equality and JavaScript by Angus Croll. - 15.5 Use braces to create blocks in case and default clauses that contain lexical declarations (e.g. let , const , function , and class ). eslint: <code>no-case-declarations</code> > Why? Lexical declarations are visible in the entire `switch` block but only get initialized when assigned, which only happens when its `case` is reached. This causes problems when multiple `case` clauses attempt to define the same thing.```javascript// badswitch (foo) { case 1: let x = 1; break; case 2: const y = 2; break; case 3: function f() { // ... } break; default: class C {}}// goodswitch (foo) { case 1: { let x = 1; break; } case 2: { const y = 2; break; } case 3: { function f() { // ... } break; } case 4: bar(); break; default: { class C {} }}``` - 15.6 Ternaries should not be nested and generally be single line expressions. eslint: <code>no-nested-ternary</code> ```javascript// badconst foo = maybe1 > maybe2 ? "bar" : value1 > value2 ? "baz" : null;// split into 2 separated ternary expressionsconst maybeNull = value1 > value2 ? 'baz' : null;// betterconst foo = maybe1 > maybe2 ? 'bar' : maybeNull;// bestconst foo = maybe1 > maybe2 ? 'bar' : maybeNull;``` - 15.7 Avoid unneeded ternary statements. eslint: <code>no-unneeded-ternary</code> ```javascript// badconst foo = a ? a : b;const bar = c ? true : false;const baz = c ? false : true;// goodconst foo = a || b;const bar = !!c;const baz = !c;``` - 15.8 When mixing operators, enclose them in parentheses. The only exception is the standard arithmetic operators: + , - , and ** since their precedence is broadly understood. We recommend enclosing / and * in parentheses because their precedence can be ambiguous when they are mixed. eslint: <code>no-mixed-operators</code> > Why? This improves readability and clarifies the developer’s intention.```javascript// badconst foo = a && b < 0 || c > 0 || d + 1 === 0;// badconst bar = a ** b - 5 % d;// bad// one may be confused into thinking (a || b) && cif (a || b && c) { return d;}// badconst bar = a + b / c * d;// goodconst foo = (a && b < 0) || c > 0 || (d + 1 === 0);// goodconst bar = a ** b - (5 % d);// goodif (a || (b && c)) { return d;}// goodconst bar = a + (b / c) * d;``` ⬆ back to top Blocks - 16.1 Use braces with all multiline blocks. eslint: <code>nonblock-statement-body-position</code> ```javascript// badif (test) return false;// goodif (test) return false;// goodif (test) { return false;}// badfunction foo() { return false; }// goodfunction bar() { return false;}``` - 16.2 If you’re using multiline blocks with if and else , put else on the same line as your if block’s closing brace. eslint: <code>brace-style</code> ```javascript// badif (test) { thing1(); thing2();}else { thing3();}// goodif (test) { thing1(); thing2();} else { thing3();}``` - 16.3 If an if block always executes a return statement, the subsequent else block is unnecessary. A return in an else if block following an if block that contains a return can be separated into multiple if blocks. eslint: <code>no-else-return</code> ```javascript// badfunction foo() { if (x) { return x; } else { return y; }}// badfunction cats() { if (x) { return x; } else if (y) { return y; }}// badfunction dogs() { if (x) { return x; } else { if (y) { return y; } }}// goodfunction foo() { if (x) { return x; } return y;}// goodfunction cats() { if (x) { return x; } if (y) { return y; }}// goodfunction dogs(x) { if (x) { if (z) { return y; } } else { return z; }}``` ⬆ back to top Control Statements - 17.1 In case your control statement ( if , while etc.) gets too long or exceeds the maximum line length, each (grouped) condition could be put into a new line. The logical operator should begin the line. > Why? Requiring operators at the beginning of the line keeps the operators aligned and follows a pattern similar to method chaining. This also improves readability by making it easier to visually follow complex logic.```javascript// badif ((foo === 123 || bar === 'abc') && doesItLookGoodWhenItBecomesThatLong() && isThisReallyHappening()) { thing1();}// badif (foo === 123 && bar === 'abc') { thing1();}// badif (foo === 123 && bar === 'abc') { thing1();}// badif ( foo === 123 && bar === 'abc') { thing1();}// goodif ( foo === 123 && bar === 'abc') { thing1();}// goodif ( (foo === 123 || bar === 'abc') && doesItLookGoodWhenItBecomesThatLong() && isThisReallyHappening()) { thing1();}// goodif (foo === 123 && bar === 'abc') { thing1();}``` - 17.2 Don't use selection operators in place of control statements. ```javascript// bad!isRunning && startRunning();// goodif (!isRunning) { startRunning();}``` ⬆ back to top Comments - 18.1 Use /** ... */ for multiline comments. ```javascript// bad// make() returns a new element// based on the passed in tag name//// @param {String} tag// @return {Element} elementfunction make(tag) { // ... return element;}// good/** * make() returns a new element * based on the passed-in tag name */function make(tag) { // ... return element;}``` - 18.2 Use // for single line comments. Place single line comments on a newline above the subject of the comment. Put an empty line before the comment unless it’s on the first line of a block. ```javascript// badconst active = true; // is current tab// good// is current tabconst active = true;// badfunction getType() { console.log('fetching type...'); // set the default type to 'no type' const type = this.type || 'no type'; return type;}// goodfunction getType() { console.log('fetching type...'); // set the default type to 'no type' const type = this.type || 'no type'; return type;}// also goodfunction getType() { // set the default type to 'no type' const type = this.type || 'no type'; return type;}``` - 18.3 Start all comments with a space to make it easier to read. eslint: <code>spaced-comment</code> ```javascript// bad//is current tabconst active = true;// good// is current tabconst active = true;// bad/** *make() returns a new element *based on the passed-in tag name */function make(tag) { // ... return element;}// good/** * make() returns a new element * based on the passed-in tag name */function make(tag) { // ... return element;}``` - 18.4 Prefixing your comments with FIXME or TODO helps other developers quickly understand if you’re pointing out a problem that needs to be revisited, or if you’re suggesting a solution to the problem that needs to be implemented. These are different than regular comments because they are actionable. The actions are FIXME: -- need to figure this out or TODO: -- need to implement . - 18.5 Use // FIXME: to annotate problems. ```javascriptclass Calculator extends Abacus { constructor() { super(); // FIXME: shouldn’t use a global here total = 0; }}``` - 18.6 Use // TODO: to annotate solutions to problems. ```javascriptclass Calculator extends Abacus { constructor() { super(); // TODO: total should be configurable by an options param this.total = 0; }}``` ⬆ back to top Whitespace - 19.1 Use soft tabs (space character) set to 2 spaces. eslint: <code>indent</code> ```javascript// badfunction foo() {∙∙∙∙let name;}// badfunction bar() {∙let name;}// goodfunction baz() {∙∙let name;}``` - 19.2 Place 1 space before the leading brace. eslint: <code>space-before-blocks</code> ```javascript// badfunction test(){ console.log('test');}// goodfunction test() { console.log('test');}// baddog.set('attr',{ age: '1 year', breed: 'Bernese Mountain Dog',});// gooddog.set('attr', { age: '1 year', breed: 'Bernese Mountain Dog',});``` - 19.3 Place 1 space before the opening parenthesis in control statements ( if , while etc.). Place no space between the argument list and the function name in function calls and declarations. eslint: <code>keyword-spacing</code> ```javascript// badif(isJedi) { fight ();}// goodif (isJedi) { fight();}// badfunction fight () { console.log ('Swooosh!');}// goodfunction fight() { console.log('Swooosh!');}``` - 19.4 Set off operators with spaces. eslint: <code>space-infix-ops</code> ```javascript// badconst x=y+5;// goodconst x = y + 5;``` - 19.5 End files with a single newline character. eslint: <code>eol-last</code> ```javascript// badimport { es6 } from './AirbnbStyleGuide'; // ...export default es6;``````javascript// badimport { es6 } from './AirbnbStyleGuide'; // ...export default es6;↵↵``````javascript// goodimport { es6 } from './AirbnbStyleGuide'; // ...export default es6;↵``` - 19.6 Use indentation when making long method chains (more than 2 method chains). Use a leading dot, which emphasizes that the line is a method call, not a new statement. eslint: <code>newline-per-chained-call</code> <code>no-whitespace-before-property</code> ```javascript// bad$('#items').find('.selected').highlight().end().find('.open').updateCount();// bad$('#items'). find('.selected'). highlight(). end(). find('.open'). updateCount();// good$('#items') .find('.selected') .highlight() .end() .find('.open') .updateCount();// badconst leds = stage.selectAll('.led').data(data).enter().append('svg:svg').classed('led', true) .attr('width', (radius + margin) * 2).append('svg:g') .attr('transform', `translate(${radius + margin},${radius + margin})`) .call(tron.led);// goodconst leds = stage.selectAll('.led') .data(data) .enter().append('svg:svg') .classed('led', true) .attr('width', (radius + margin) * 2) .append('svg:g') .attr('transform', `translate(${radius + margin},${radius + margin})`) .call(tron.led);// goodconst leds = stage.selectAll('.led').data(data);const svg = leds.enter().append('svg:svg');svg.classed('led', true).attr('width', (radius + margin) * 2);const g = svg.append('svg:g');g.attr('transform', `translate(${radius + margin},${radius + margin})`).call(tron.led);``` - 19.7 Leave a blank line after blocks and before the next statement. ```javascript// badif (foo) { return bar;}return baz;// goodif (foo) { return bar;}return baz;// badconst obj = { foo() { }, bar() { },};return obj;// goodconst obj = { foo() { }, bar() { },};return obj;// badconst arr = [ function foo() { }, function bar() { },];return arr;// goodconst arr = [ function foo() { }, function bar() { },];return arr;``` - 19.8 Do not pad your blocks with blank lines. eslint: <code>padded-blocks</code> ```javascript// badfunction bar() { console.log(foo);}// badif (baz) { console.log(qux);} else { console.log(foo);}// badclass Foo { constructor(bar) { this.bar = bar; }}// goodfunction bar() { console.log(foo);}// goodif (baz) { console.log(qux);} else { console.log(foo);}``` - 19.9 Do not use multiple blank lines to pad your code. eslint: <code>no-multiple-empty-lines</code> <!-- markdownlint-disable MD012 -->```javascript// badclass Person { constructor(fullName, email, birthday) { this.fullName = fullName; this.email = email; this.setAge(birthday); } setAge(birthday) { const today = new Date(); const age = this.getAge(today, birthday); this.age = age; } getAge(today, birthday) { // .. }}// goodclass Person { constructor(fullName, email, birthday) { this.fullName = fullName; this.email = email; this.setAge(birthday); } setAge(birthday) { const today = new Date(); const age = getAge(today, birthday); this.age = age; } getAge(today, birthday) { // .. }}``` - 19.10 Do not add spaces inside parentheses. eslint: <code>space-in-parens</code> ```javascript// badfunction bar( foo ) { return foo;}// goodfunction bar(foo) { return foo;}// badif ( foo ) { console.log(foo);}// goodif (foo) { console.log(foo);}``` - 19.11 Do not add spaces inside brackets. eslint: <code>array-bracket-spacing</code> ```javascript// badconst foo = [ 1, 2, 3 ];console.log(foo[ 0 ]);// goodconst foo = [1, 2, 3];console.log(foo[0]);``` - 19.12 Add spaces inside curly braces. eslint: <code>object-curly-spacing</code> ```javascript// badconst foo = {clark: 'kent'};// goodconst foo = { clark: 'kent' };``` - 19.13 Avoid having lines of code that are longer than 100 characters (including whitespace). Note: per above , long strings are exempt from this rule, and should not be broken up. eslint: <code>max-len</code> > Why? This ensures readability and maintainability.```javascript// badconst foo = jsonData && jsonData.foo && jsonData.foo.bar && jsonData.foo.bar.baz && jsonData.foo.bar.baz.quux && jsonData.foo.bar.baz.quux.xyzzy;// bad$.ajax({ method: 'POST', url: 'https://airbnb.com/', data: { name: 'John' } }).done(() => console.log('Congratulations!')).fail(() => console.log('You have failed this city.'));// goodconst foo = jsonData && jsonData.foo && jsonData.foo.bar && jsonData.foo.bar.baz && jsonData.foo.bar.baz.quux && jsonData.foo.bar.baz.quux.xyzzy;// good$.ajax({ method: 'POST', url: 'https://airbnb.com/', data: { name: 'John' },}) .done(() => console.log('Congratulations!')) .fail(() => console.log('You have failed this city.'));``` - 19.14 Require consistent spacing inside an open block token and the next token on the same line. This rule also enforces consistent spacing inside a close block token and previous token on the same line. eslint: <code>block-spacing</code> ```javascript// badfunction foo() {return true;}if (foo) { bar = 0;}// goodfunction foo() { return true; }if (foo) { bar = 0; }``` - 19.15 Avoid spaces before commas and require a space after commas. eslint: <code>comma-spacing</code> ```javascript// badvar foo = 1,bar = 2;var arr = [1 , 2];// goodvar foo = 1, bar = 2;var arr = [1, 2];``` - 19.16 Enforce spacing inside of computed property brackets. eslint: <code>computed-property-spacing</code> ```javascript// badobj[foo ]obj[ 'foo']var x = {[ b ]: a}obj[foo[ bar ]]// goodobj[foo]obj['foo']var x = { [b]: a }obj[foo[bar]]``` - 19.17 Avoid spaces between functions and their invocations. eslint: <code>func-call-spacing</code> ```javascript// badfunc ();func();// goodfunc();``` - 19.18 Enforce spacing between keys and values in object literal properties. eslint: <code>key-spacing</code> ```javascript// badvar obj = { foo : 42 };var obj2 = { foo:42 };// goodvar obj = { foo: 42 };``` - 19.19 Avoid trailing spaces at the end of lines. eslint: <code>no-trailing-spaces</code> - 19.20 Avoid multiple empty lines, only allow one newline at the end of files, and avoid a newline at the beginning of files. eslint: <code>no-multiple-empty-lines</code> <!-- markdownlint-disable MD012 -->```javascript// bad - multiple empty linesvar x = 1;var y = 2;// bad - 2+ newlines at end of filevar x = 1;var y = 2;// bad - 1+ newline(s) at beginning of filevar x = 1;var y = 2;// goodvar x = 1;var y = 2;```<!-- markdownlint-enable MD012 --> ⬆ back to top Commas - 20.1 Leading commas: Nope. eslint: <code>comma-style</code> ```javascript// badconst story = [ once , upon , aTime];// goodconst story = [ once, upon, aTime,];// badconst hero = { firstName: 'Ada' , lastName: 'Lovelace' , birthYear: 1815 , superPower: 'computers'};// goodconst hero = { firstName: 'Ada', lastName: 'Lovelace', birthYear: 1815, superPower: 'computers',};``` - 20.2 Additional trailing comma: Yup. eslint: <code>comma-dangle</code> > Why? This leads to cleaner git diffs. Also, transpilers like Babel will remove the additional trailing comma in the transpiled code which means you don’t have to worry about the [trailing comma problem](https://github.com/airbnb/javascript/blob/es5-deprecated/es5/README.md#commas) in legacy browsers.```diff// bad - git diff without trailing commaconst hero = { firstName: 'Florence',- lastName: 'Nightingale'+ lastName: 'Nightingale',+ inventorOf: ['coxcomb chart', 'modern nursing']};// good - git diff with trailing commaconst hero = { firstName: 'Florence', lastName: 'Nightingale',+ inventorOf: ['coxcomb chart', 'modern nursing'],};``````javascript// badconst hero = { firstName: 'Dana', lastName: 'Scully'};const heroes = [ 'Batman', 'Superman'];// goodconst hero = { firstName: 'Dana', lastName: 'Scully',};const heroes = [ 'Batman', 'Superman',];// badfunction createHero( firstName, lastName, inventorOf) { // does nothing}// goodfunction createHero( firstName, lastName, inventorOf,) { // does nothing}// good (note that a comma must not appear after a "rest" element)function createHero( firstName, lastName, inventorOf, ...heroArgs) { // does nothing}// badcreateHero( firstName, lastName, inventorOf);// goodcreateHero( firstName, lastName, inventorOf,);// good (note that a comma must not appear after a "rest" element)createHero( firstName, lastName, inventorOf, ...heroArgs);``` ⬆ back to top Semicolons - 21.1 Yup. eslint: <code>semi</code> > Why? When JavaScript encounters a line break without a semicolon, it uses a set of rules called [Automatic Semicolon Insertion](https://tc39.github.io/ecma262/#sec-automatic-semicolon-insertion) to determine whether it should regard that line break as the end of a statement, and (as the name implies) place a semicolon into your code before the line break if it thinks so. ASI contains a few eccentric behaviors, though, and your code will break if JavaScript misinterprets your line break. These rules will become more complicated as new features become a part of JavaScript. Explicitly terminating your statements and configuring your linter to catch missing semicolons will help prevent you from encountering issues.```javascript// bad - raises exceptionconst luke = {}const leia = {}[luke, leia].forEach((jedi) => jedi.father = 'vader')// bad - raises exceptionconst reaction = "No! That’s impossible!"(async function meanwhileOnTheFalcon() { // handle `leia`, `lando`, `chewie`, `r2`, `c3p0` // ...}())// bad - returns `undefined` instead of the value on the next line - always happens when `return` is on a line by itself because of ASI!function foo() { return 'search your feelings, you know it to be foo'}// goodconst luke = {};const leia = {};[luke, leia].forEach((jedi) => { jedi.father = 'vader';});// goodconst reaction = "No! That’s impossible!";(async function meanwhileOnTheFalcon() { // handle `leia`, `lando`, `chewie`, `r2`, `c3p0` // ...}());// goodfunction foo() { return 'search your feelings, you know it to be foo';}```[Read more](https://stackoverflow.com/questions/7365172/semicolon-before-self-invoking-function/7365214#7365214). ⬆ back to top Type Casting & Coercion - 22.1 Perform type coercion at the beginning of the statement. - 22.2 Strings: eslint: <code>no-new-wrappers</code> ```javascript// => this.reviewScore = 9;// badconst totalScore = new String(this.reviewScore); // typeof totalScore is "object" not "string"// badconst totalScore = this.reviewScore + ''; // invokes this.reviewScore.valueOf()// badconst totalScore = this.reviewScore.toString(); // isn’t guaranteed to return a string// goodconst totalScore = String(this.reviewScore);``` - 22.3 Numbers: Use Number for type casting and parseInt always with a radix for parsing strings. eslint: <code>radix</code> <code>no-new-wrappers</code> > Why? The `parseInt` function produces an integer value dictated by interpretation of the contents of the string argument according to the specified radix. Leading whitespace in string is ignored. If radix is `undefined` or `0`, it is assumed to be `10` except when the number begins with the character pairs `0x` or `0X`, in which case a radix of 16 is assumed. This differs from ECMAScript 3, which merely discouraged (but allowed) octal interpretation. Many implementations have not adopted this behavior as of 2013. And, because older browsers must be supported, always specify a radix.```javascriptconst inputValue = '4';// badconst val = new Number(inputValue);// badconst val = +inputValue;// badconst val = inputValue >> 0;// badconst val = parseInt(inputValue);// goodconst val = Number(inputValue);// goodconst val = parseInt(inputValue, 10);``` - 22.4 If for whatever reason you are doing something wild and parseInt is your bottleneck and need to use Bitshift for performance reasons , leave a comment explaining why and what you’re doing. ```javascript// good/** * parseInt was the reason my code was slow. * Bitshifting the String to coerce it to a * Number made it a lot faster. */const val = inputValue >> 0;``` - 22.5 Note: Be careful when using bitshift operations. Numbers are represented as 64-bit values , but bitshift operations always return a 32-bit integer ( source ). Bitshift can lead to unexpected behavior for integer values larger than 32 bits. Discussion . Largest signed 32-bit Int is 2,147,483,647: ```javascript2147483647 >> 0; // => 21474836472147483648 >> 0; // => -21474836482147483649 >> 0; // => -2147483647``` - 22.6 Booleans: eslint: <code>no-new-wrappers</code> ```javascriptconst age = 0;// badconst hasAge = new Boolean(age);// goodconst hasAge = Boolean(age);// bestconst hasAge = !!age;``` ⬆ back to top Naming Conventions - 23.1 Avoid single letter names. Be descriptive with your naming. eslint: <code>id-length</code> ```javascript// badfunction q() { // ...}// goodfunction query() { // ...}``` - 23.2 Use camelCase when naming objects, functions, and instances. eslint: <code>camelcase</code> ```javascript// badconst OBJEcttsssss = {};const this_is_my_object = {};function c() {}// goodconst thisIsMyObject = {};function thisIsMyFunction() {}``` - 23.3 Use PascalCase only when naming constructors or classes. eslint: <code>new-cap</code> ```javascript// badfunction user(options) { this.name = options.name;}const bad = new user({ name: 'nope',});// goodclass User { constructor(options) { this.name = options.name; }}const good = new User({ name: 'yup',});``` - 23.4 Do not use trailing or leading underscores. eslint: <code>no-underscore-dangle</code> > Why? JavaScript does not have the concept of privacy in terms of properties or methods. Although a leading underscore is a common convention to mean “private”, in fact, these properties are fully public, and as such, are part of your public API contract. This convention might lead developers to wrongly think that a change won’t count as breaking, or that tests aren’t needed. tl;dr: if you want something to be “private”, it must not be observably present.```javascript// badthis.__firstName__ = 'Panda';this.firstName_ = 'Panda';this._firstName = 'Panda';// goodthis.firstName = 'Panda';// good, in environments where WeakMaps are available// see https://kangax.github.io/compat-table/es6/#test-WeakMapconst firstNames = new WeakMap();firstNames.set(this, 'Panda');``` - 23.5 Don’t save references to this . Use arrow functions or Function#bind . ```javascript// badfunction foo() { const self = this; return function () { console.log(self); };}// badfunction foo() { const that = this; return function () { console.log(that); };}// goodfunction foo() { return () => { console.log(this); };}``` - 23.6 A base filename should exactly match the name of its default export. ```javascript// file 1 contentsclass CheckBox { // ...}export default CheckBox;// file 2 contentsexport default function fortyTwo() { return 42; }// file 3 contentsexport default function insideDirectory() {}// in some other file// badimport CheckBox from './checkBox'; // PascalCase import/export, camelCase filenameimport FortyTwo from './FortyTwo'; // PascalCase import/filename, camelCase exportimport InsideDirectory from './InsideDirectory'; // PascalCase import/filename, camelCase export// badimport CheckBox from './check_box'; // PascalCase import/export, snake_case filenameimport forty_two from './forty_two'; // snake_case import/filename, camelCase exportimport inside_directory from './inside_directory'; // snake_case import, camelCase exportimport index from './inside_directory/index'; // requiring the index file explicitlyimport insideDirectory from './insideDirectory/index'; // requiring the index file explicitly// goodimport CheckBox from './CheckBox'; // PascalCase export/import/filenameimport fortyTwo from './fortyTwo'; // camelCase export/import/filenameimport insideDirectory from './insideDirectory'; // camelCase export/import/directory name/implicit "index"// ^ supports both insideDirectory.js and insideDirectory/index.js``` - 23.7 Use camelCase when you export-default a function. Your filename should be identical to your function’s name. ```javascriptfunction makeStyleGuide() { // ...}export default makeStyleGuide;``` - 23.8 Use PascalCase when you export a constructor / class / singleton / function library / bare object. ```javascriptconst AirbnbStyleGuide = { es6: { },};export default AirbnbStyleGuide;``` - 23.9 Acronyms and initialisms should always be all uppercased, or all lowercased. > Why? Names are for readability, not to appease a computer algorithm.```javascript// badimport SmsContainer from './containers/SmsContainer';// badconst HttpRequests = [ // ...];// goodimport SMSContainer from './containers/SMSContainer';// goodconst HTTPRequests = [ // ...];// also goodconst httpRequests = [ // ...];// bestimport TextMessageContainer from './containers/TextMessageContainer';// bestconst requests = [ // ...];``` - 23.10 You may optionally uppercase a constant only if it (1) is exported, (2) is a const (it can not be reassigned), and (3) the programmer can trust it (and its nested properties) to never change. > Why? This is an additional tool to assist in situations where the programmer would be unsure if a variable might ever change. UPPERCASE_VARIABLES are letting the programmer know that they can trust the variable (and its properties) not to change.- What about all `const` variables? - This is unnecessary, so uppercasing should not be used for constants within a file. It should be used for exported constants however.- What about exported objects? - Uppercase at the top level of export (e.g. `EXPORTED_OBJECT.key`) and maintain that all nested properties do not change.```javascript// badconst PRIVATE_VARIABLE = 'should not be unnecessarily uppercased within a file';// badexport const THING_TO_BE_CHANGED = 'should obviously not be uppercased';// badexport let REASSIGNABLE_VARIABLE = 'do not use let with uppercase variables';// ---// allowed but does not supply semantic valueexport const apiKey = 'SOMEKEY';// better in most casesexport const API_KEY = 'SOMEKEY';// ---// bad - unnecessarily uppercases key while adding no semantic valueexport const MAPPING = { KEY: 'value'};// goodexport const MAPPING = { key: 'value'};``` ⬆ back to top Accessors - 24.1 Accessor functions for properties are not required. - 24.2 Do not use JavaScript getters/setters as they cause unexpected side effects and are harder to test, maintain, and reason about. Instead, if you do make accessor functions, use getVal() and setVal('hello') . ```javascript// badclass Dragon { get age() { // ... } set age(value) { // ... }}// goodclass Dragon { getAge() { // ... } setAge(value) { // ... }}``` - 24.3 If the property/method is a boolean , use isVal() or hasVal() . ```javascript// badif (!dragon.age()) { return false;}// goodif (!dragon.hasAge()) { return false;}``` - 24.4 It’s okay to create get() and set() functions, but be consistent. ```javascriptclass Jedi { constructor(options = {}) { const lightsaber = options.lightsaber || 'blue'; this.set('lightsaber', lightsaber); } set(key, val) { this[key] = val; } get(key) { return this[key]; }}``` ⬆ back to top Events - 25.1 When attaching data payloads to events (whether DOM events or something more proprietary like Backbone events), pass an object literal (also known as a "hash") instead of a raw value. This allows a subsequent contributor to add more data to the event payload without finding and updating every handler for the event. For example, instead of: ```javascript// bad$(this).trigger('listingUpdated', listing.id);// ...$(this).on('listingUpdated', (e, listingID) => { // do something with listingID});```prefer:```javascript// good$(this).trigger('listingUpdated', { listingID: listing.id });// ...$(this).on('listingUpdated', (e, data) => { // do something with data.listingID});``` ⬆ back to top jQuery - 26.1 Prefix jQuery object variables with a $ . ```javascript// badconst sidebar = $('.sidebar');// goodconst $sidebar = $('.sidebar');// goodconst $sidebarBtn = $('.sidebar-btn');``` - 26.2 Cache jQuery lookups. ```javascript// badfunction setSidebar() { $('.sidebar').hide(); // ... $('.sidebar').css({ 'background-color': 'pink', });}// goodfunction setSidebar() { const $sidebar = $('.sidebar'); $sidebar.hide(); // ... $sidebar.css({ 'background-color': 'pink', });}``` - 26.3 For DOM queries use Cascading $('.sidebar ul') or parent > child $('.sidebar > ul') . jsPerf - 26.4 Use find with scoped jQuery object queries. ```javascript// bad$('ul', '.sidebar').hide();// bad$('.sidebar').find('ul').hide();// good$('.sidebar ul').hide();// good$('.sidebar > ul').hide();// good$sidebar.find('ul').hide();``` ⬆ back to top ECMAScript 5 Compatibility - 27.1 Refer to Kangax ’s ES5 compatibility table . ⬆ back to top ECMAScript 6+ (ES 2015+) Styles - 28.1 This is a collection of links to the various ES6+ features. Arrow Functions Classes Object Shorthand Object Concise Object Computed Properties Template Strings Destructuring Default Parameters Rest Array Spreads Let and Const Exponentiation Operator Iterators and Generators Modules 28.2 Do not use TC39 proposals that have not reached stage 3. Why? They are not finalized , and they are subject to change or to be withdrawn entirely. We want to use JavaScript, and proposals are not JavaScript yet. ⬆ back to top Standard Library The Standard Library contains utilities that are functionally broken but remain for legacy reasons. - 29.1 Use Number.isNaN instead of global isNaN . eslint: <code>no-restricted-globals</code> > Why? The global `isNaN` coerces non-numbers to numbers, returning true for anything that coerces to NaN.> If this behavior is desired, make it explicit.```javascript// badisNaN('1.2'); // falseisNaN('1.2.3'); // true// goodNumber.isNaN('1.2.3'); // falseNumber.isNaN(Number('1.2.3')); // true``` - 29.2 Use Number.isFinite instead of global isFinite . eslint: <code>no-restricted-globals</code> > Why? The global `isFinite` coerces non-numbers to numbers, returning true for anything that coerces to a finite number.> If this behavior is desired, make it explicit.```javascript// badisFinite('2e3'); // true// goodNumber.isFinite('2e3'); // falseNumber.isFinite(parseInt('2e3', 10)); // true``` ⬆ back to top Testing - 30.1 Yup. ```javascriptfunction foo() { return true;}``` - 30.2 No, but seriously : - Whichever testing framework you use, you should be writing tests! - Strive to write many small pure functions, and minimize where mutations occur. - Be cautious about stubs and mocks - they can make your tests more brittle. - We primarily use <code>mocha</code> and <code>jest</code> at Airbnb. <code>tape</code> is also used occasionally for small, separate modules. - 100% test coverage is a good goal to strive for, even if it’s not always practical to reach it. - Whenever you fix a bug, write a regression test . A bug fixed without a regression test is almost certainly going to break again in the future. ⬆ back to top Performance On Layout & Web Performance String vs Array Concat Try/Catch Cost In a Loop Bang Function jQuery Find vs Context, Selector innerHTML vs textContent for script text Long String Concatenation Are JavaScript functions like <code>map()</code>, <code>reduce()</code>, and <code>filter()</code> optimized for traversing arrays? Loading... ⬆ back to top Resources Learning ES6+ Latest ECMA spec ExploringJS ES6 Compatibility Table Comprehensive Overview of ES6 Features Read This Standard ECMA-262 Tools Code Style Linters ESlint - Airbnb Style .eslintrc JSHint - Airbnb Style .jshintrc Neutrino Preset - @neutrinojs/airbnb Other Style Guides Google JavaScript Style Guide Google JavaScript Style Guide (Old) jQuery Core Style Guidelines Principles of Writing Consistent, Idiomatic JavaScript StandardJS Other Styles Naming this in nested functions - Christian Johansen Conditional Callbacks - Ross Allen Popular JavaScript Coding Conventions on GitHub - JeongHoon Byun Multiple var statements in JavaScript, not superfluous - Ben Alman Further Reading Understanding JavaScript Closures - Angus Croll Basic JavaScript for the impatient programmer - Dr. Axel Rauschmayer You Might Not Need jQuery - Zack Bloom & Adam Schwartz ES6 Features - Luke Hoban Frontend Guidelines - Benjamin De Cock Books JavaScript: The Good Parts - Douglas Crockford JavaScript Patterns - Stoyan Stefanov Pro JavaScript Design Patterns - Ross Harmes and Dustin Diaz High Performance Web Sites: Essential Knowledge for Front-End Engineers - Steve Souders Maintainable JavaScript - Nicholas C. Zakas JavaScript Web Applications - Alex MacCaw Pro JavaScript Techniques - John Resig Smashing Node.js: JavaScript Everywhere - Guillermo Rauch Secrets of the JavaScript Ninja - John Resig and Bear Bibeault Human JavaScript - Henrik Joreteg Superhero.js - Kim Joar Bekkelund, Mads Mobæk, & Olav Bjorkoy JSBooks - Julien Bouquillon Third Party JavaScript - Ben Vinegar and Anton Kovalyov Effective JavaScript: 68 Specific Ways to Harness the Power of JavaScript - David Herman Eloquent JavaScript - Marijn Haverbeke You Don’t Know JS: ES6 & Beyond - Kyle Simpson Blogs JavaScript Weekly JavaScript, JavaScript... Bocoup Weblog Adequately Good NCZOnline Perfection Kills Ben Alman Dmitry Baranovskiy nettuts Podcasts JavaScript Air JavaScript Jabber ⬆ back to top In the Wild This is a list of organizations that are using this style guide. Send us a pull request and we'll add you to the list. 123erfasst : 123erfasst/javascript 4Catalyzer : 4Catalyzer/javascript Aan Zee : AanZee/javascript Airbnb : airbnb/javascript AloPeyk : AloPeyk AltSchool : AltSchool/javascript Apartmint : apartmint/javascript Ascribe : ascribe/javascript Avant : avantcredit/javascript Axept : axept/javascript Billabong : billabong/javascript Bisk : bisk Bonhomme : bonhommeparis/javascript Brainshark : brainshark/javascript CaseNine : CaseNine/javascript Cerner : Cerner Chartboost : ChartBoost/javascript-style-guide Coeur d'Alene Tribe : www.cdatribe-nsn.gov ComparaOnline : comparaonline/javascript Compass Learning : compasslearning/javascript-style-guide DailyMotion : dailymotion/javascript DoSomething : DoSomething/eslint-config Digitpaint digitpaint/javascript Drupal : www.drupal.org Ecosia : ecosia/javascript Evernote : evernote/javascript-style-guide Evolution Gaming : evolution-gaming/javascript EvozonJs : evozonjs/javascript ExactTarget : ExactTarget/javascript Flexberry : Flexberry/javascript-style-guide Gawker Media : gawkermedia General Electric : GeneralElectric/javascript Generation Tux : GenerationTux/javascript GoodData : gooddata/gdc-js-style GreenChef : greenchef/javascript Grooveshark : grooveshark/javascript Grupo-Abraxas : Grupo-Abraxas/javascript Happeo : happeo/javascript Honey : honeyscience/javascript How About We : howaboutwe/javascript HubSpot : HubSpot/javascript Hyper : hyperoslo/javascript-playbook InterCity Group : intercitygroup/javascript-style-guide Jam3 : Jam3/Javascript-Code-Conventions JSSolutions : JSSolutions/javascript Kaplan Komputing : kaplankomputing/javascript KickorStick : kickorstick Kinetica Solutions : kinetica/javascript LEINWAND : LEINWAND/javascript Lonely Planet : lonelyplanet/javascript M2GEN : M2GEN/javascript Mighty Spring : mightyspring/javascript MinnPost : MinnPost/javascript MitocGroup : MitocGroup/javascript Muber : muber National Geographic : natgeo NullDev : NullDevCo/JavaScript-Styleguide Nulogy : nulogy/javascript Orange Hill Development : orangehill/javascript Orion Health : orionhealth/javascript OutBoxSoft : OutBoxSoft/javascript Peerby : Peerby/javascript Pier 1 : Pier1/javascript Qotto : Qotto/javascript-style-guide React : facebook.github.io/react/contributing/how-to-contribute.html#style-guide REI : reidev/js-style-guide Ripple : ripple/javascript-style-guide Sainsbury’s Supermarkets : jsainsburyplc Shutterfly : shutterfly/javascript Sourcetoad : sourcetoad/javascript Springload : springload StratoDem Analytics : stratodem/javascript SteelKiwi Development : steelkiwi/javascript StudentSphere : studentsphere/javascript SwoopApp : swoopapp/javascript SysGarage : sysgarage/javascript-style-guide Syzygy Warsaw : syzygypl/javascript Target : target/javascript Terra : terra TheLadders : TheLadders/javascript The Nerdery : thenerdery/javascript-standards Tomify : tomprats Traitify : traitify/eslint-config-traitify T4R Technology : T4R-Technology/javascript UrbanSim : urbansim VoxFeed : VoxFeed/javascript-style-guide WeBox Studio : weboxstudio/javascript Weggo : Weggo/javascript Zillow : zillow/javascript ZocDoc : ZocDoc/javascript ⬆ back to top Translation This style guide is also available in other languages: Brazilian Portuguese : armoucar/javascript-style-guide Bulgarian : borislavvv/javascript Catalan : fpmweb/javascript-style-guide Chinese (Simplified) : lin-123/javascript Chinese (Traditional) : jigsawye/javascript French : nmussy/javascript-style-guide German : timofurrer/javascript-style-guide Italian : sinkswim/javascript-style-guide Japanese : mitsuruog/javascript-style-guide Korean : ParkSB/javascript-style-guide Russian : leonidlebedev/javascript-airbnb Spanish : paolocarrasco/javascript-style-guide Thai : lvarayut/javascript-style-guide Turkish : eraycetinay/javascript Ukrainian : ivanzusko/javascript Vietnam : dangkyokhoang/javascript-style-guide The JavaScript Style Guide Guide Reference Chat With Us About JavaScript Find us on gitter . Contributors View Contributors License (The MIT License) Copyright (c) 2012 Airbnb Permission is hereby granted, free of charge, to any person obtaininga copy of this software and associated documentation files (the'Software'), to deal in the Software without restriction, includingwithout limitation the rights to use, copy, modify, merge, publish,distribute, sublicense, and/or sell copies of the Software, and topermit persons to whom the Software is furnished to do so, subject tothe following conditions: The above copyright notice and this permission notice shall beincluded in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OFMERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANYCLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THESOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. ⬆ back to top Amendments We encourage you to fork this guide and change the rules to fit your team’s style guide. Below, you may list some amendments to the style guide. This allows you to periodically update your style guide without having to deal with merge conflicts. }; To restore the repository download the bundle wget https://archive.org/download/github.com-airbnb-javascript_-_2022-05-26_04-23-02/airbnb-javascript_-_2022-05-26_04-23-02.bundle and run: git clone airbnb-javascript_-_2022-05-26_04-23-02.bundle Source: https://github.com/airbnb/javascript Uploader: airbnb Upload date: 2022-05-26

Microsoft Programming in HTML5 with JavaScript and CSS3

30+ Web Projects with HTML, CSS, and JavaScript

Curso completo de Desenvolvimento Web Crie 6 projetosHTML JAVASCRIPT CSS PHP 14. Orientação a objetos PHP 1. Introdução

For all programmer Logotype of HTML5, CSS3 and JAVASCRIPT

This program converts Javascript source code into scrambled and unreadable form, preventing it from being analyzed and stolen. It can process Javascript tags in HTML files and all files associated with HTML pages, as well as separate Javascript files. It can remove comments and white spaces and pack the code as a long line. You can add finishing semicolons when appropriate, create a list of function and variable names, and generate new names.

This program converts Javascript source code into scrambled and unreadable form, preventing it from being analyzed and stolen. It can process Javascript tags in HTML files and all files associated with HTML pages, as well as separate Javascript files. It can remove comments and white spaces and pack the code as a long line. You can add finishing semicolons when appropriate, create a list of function and variable names, and generate new names.

Algorithms and Data Structures implemented in JavaScript for beginners, following best practices. The Algorithms - JavaScript JavaScript Repository of TheAlgorithms, which implements various algorithms and data structures in JavaScript. [![JavaScript Banner][banner]](DIRECTORY.md) [![Language grade: JavaScript][grade]][lgtm] [![Checks][checks]][actions] [![Contributions Welcome][welcome]](CONTRIBUTING.md) [![standard.js][standard-logo]][standard-js] [![Discord chat][chat]][discord-server] These implementations are for demonstrative purposes only. Dedicated implementations of these algorithms and data structures are much better for performance and security reasons. We also do not provide any guarantee for api stability. Before contributing to this repository, make sure to read our Contribution Guidelines . You can lookat other TheAlgorithms Repositories or the issues with a "help wanted" label forinspiration regarding what to implement. Our maintainers will guide you through how to make your contribution properlyif you make any mistakes. The names of the maintainers of this repository is listed in the CODEOWNERS file . You can find a list of the algorithms currently in the repository in the directory . Explanations ofmany of the algorithms can be found in the wiki . To restore the repository download the bundle wget https://archive.org/download/github.com-TheAlgorithms-JavaScript_-_2022-07-19_04-10-17/TheAlgorithms-JavaScript_-_2022-07-19_04-10-17.bundle and run: git clone TheAlgorithms-JavaScript_-_2022-07-19_04-10-17.bundle Source: https://github.com/TheAlgorithms/JavaScript Uploader: TheAlgorithms Upload date: 2022-07-19

This talk occurred at DWeb Camp 2023 at Camp Navarro, CA. It was given by Tracey Jaquith. Link to SCHED The first five minutes of this talk are dedicated to explaining the idea, showing a post, and explaining how the simple markdown becomes a full website. Then the speaker will explain the benefits of this approach, explaining what a sitemap is, and how it's used. After that, we'll take a look at some of the JavaScript code that parses the posts, creates the site theme, and transforms the content. Speaker Tracey Jaquith, TV Architect & DevOps: Tracey was a founding coder and system architect for Internet Archive in 1996, writing multi-threaded servers, crawlers and more.  In 2000, Tracey left for four years to follow her Cornell mentor, Dan Huttenlocher, and was a technical lead and founding engineer at a startup. Recently, she rewrote Archive's TV recording system to an opensource single server system, capable of 75 simultaneous 24x7 channels, made the TV site "full stack" first and second versions, and brought archive.org website to "version 2".  Tracey is now leading the containerization of the Internet Archive, holding a Master's and Bachelor's in computer science from Cornell University where she focused on machine vision and robotics.

Curso completo de Desenvolvimento Web Crie 6 projetosHTML JAVASCRIPT CSS PHP 2. Preparando-se para o desenvolvimento 6. Como exibir as extensões dos arquivos

Video content can be found here: https://www.youtube.com/channel/UC0BAd8tPlDqFvDYBemHcQPQ/

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Part 1 is here. In this video, I go through the remaining arrays exercises in Launch School's Introduction to Programming JavaScript book. These exercises are meant to be repeated often in order to solidify one's understanding of JavaScript fundamentals.

Part 1 is here. In this video, I go through the remaining arrays exercises in Launch School's Introduction to Programming JavaScript book. These exercises are meant to be repeated often in order to solidify one's understanding of JavaScript fundamentals.

This time on the show, pound include programming dot h! We're going to void main and Hello World all up in this biznitch. Python, JavaScript, BASIC? It's time to learn to code! All that and more this time on Hak5............return zero Source: https://www.youtube.com/watch?v=tQBmdlz3sF4 Uploader: Hak5

Zum JavaScript Kurs: https://bit.ly/3Znn27a In diesem Video wirst du lernen, wie man die JavsScript Map Function verwendet. Dieses umfangreiche JavaScript Map Function Tutorial auf Deutsch bringt dir alles bei, was du über die JavaScript Map Function wissen musst. -------------------------------------------------------------------------------- Möchtest du mehr Inhalte von Programmieren Starten haben? Hier findest du hilfreiche Links für unsere wertvollsten Ressourcen: Besuche unsere Webseite: https://programmieren-starten.de/?utm_source=youtube&utm_medium=social&utm_term=javascript-map-function-tutorial&utm_content=link-in-videobeschreibung&utm_campaign=value Kurse einzeln kaufen: https://programmieren-starten.de/produkte/?utm_source=youtube&utm_medium=social&utm_term=javascript-map-function-tutorial&utm_content=link-in-videobeschreibung&utm_campaign=einzelkauf Besuche unseren Blog: https://programmieren-starten.de/blog/?utm_source=youtube&utm_medium=social&utm_term=javascript-map-function-tutorial&utm_content=link-in-videobeschreibung&utm_campaign=value

Zum JavaScript Kurs: https://bit.ly/3Znn27a In diesem Video wirst du lernen, wie man die JavsScript Map Function verwendet. Dieses umfangreiche JavaScript Map Function Tutorial auf Deutsch bringt dir alles bei, was du über die JavaScript Map Function wissen musst. -------------------------------------------------------------------------------- Möchtest du mehr Inhalte von Programmieren Starten haben? Hier findest du hilfreiche Links für unsere wertvollsten Ressourcen: Besuche unsere Webseite: https://programmieren-starten.de/?utm_source=youtube&utm_medium=social&utm_term=javascript-map-function-tutorial&utm_content=link-in-videobeschreibung&utm_campaign=value Kurse einzeln kaufen: https://programmieren-starten.de/produkte/?utm_source=youtube&utm_medium=social&utm_term=javascript-map-function-tutorial&utm_content=link-in-videobeschreibung&utm_campaign=einzelkauf Besuche unseren Blog: https://programmieren-starten.de/blog/?utm_source=youtube&utm_medium=social&utm_term=javascript-map-function-tutorial&utm_content=link-in-videobeschreibung&utm_campaign=value

Zum JavaScript Kurs: https://bit.ly/3Znn27a In diesem Video wirst du lernen, wie man die JavsScript Map Function verwendet. Dieses umfangreiche JavaScript Map Function Tutorial auf Deutsch bringt dir alles bei, was du über die JavaScript Map Function wissen musst. -------------------------------------------------------------------------------- Möchtest du mehr Inhalte von Programmieren Starten haben? Hier findest du hilfreiche Links für unsere wertvollsten Ressourcen: Besuche unsere Webseite: https://programmieren-starten.de/?utm_source=youtube&utm_medium=social&utm_term=javascript-map-function-tutorial&utm_content=link-in-videobeschreibung&utm_campaign=value Kurse einzeln kaufen: https://programmieren-starten.de/produkte/?utm_source=youtube&utm_medium=social&utm_term=javascript-map-function-tutorial&utm_content=link-in-videobeschreibung&utm_campaign=einzelkauf Besuche unseren Blog: https://programmieren-starten.de/blog/?utm_source=youtube&utm_medium=social&utm_term=javascript-map-function-tutorial&utm_content=link-in-videobeschreibung&utm_campaign=value

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துவக்க நிலையாளர்களுக்கான ஜாவாஉரைநிரல்(JavaScript) - ச. குப்பன்

துவக்க நிலையாளர்களுக்கான ஜாவாஉரைநிரல்(JavaScript) - ச. குப்பன்

துவக்க நிலையாளர்களுக்கான ஜாவாஉரைநிரல்(JavaScript) - ச. குப்பன்

Video content can be found here: https://www.youtube.com/channel/UC0BAd8tPlDqFvDYBemHcQPQ/