Airbnb JavaScript Style Guide() {A mostly reasonable approach to JavaScript
For the ES5-only guide click here.
1.1 Primitives: When you access a primitive type you work directly on its value.
stringnumberbooleannullundefinedconst foo = 1; let bar = foo; bar = 9; console.log(foo, bar); // => 1, 9
1.2 Complex: When you access a complex type you work on a reference to its value.
objectarrayfunctionconst foo = [1, 2]; const bar = foo; bar[0] = 9; console.log(foo[0], bar[0]); // => 9, 9
const for all of your references; avoid using var.Why? This ensures that you can't reassign your references (mutation), which can lead to bugs and difficult to comprehend code.
```javascript
// bad
var a = 1;
var b = 2;
// good
const a = 1;
const b = 2;
```
let instead of var.Why?
letis block-scoped rather than function-scoped likevar.
```javascript
// bad
var 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.
// const and let only exist in the blocks they are defined in.
{
let a = 1;
const b = 1;
}
console.log(a); // ReferenceError
console.log(b); // ReferenceError3.1 Use the literal syntax for object creation.
// bad
const item = new Object();
// good
const item = {};3.2 Don't use reserved words as keys. It won't work in IE8. More info.
// bad
const superman = {
default: { clark: 'kent' },
private: true
};
// good
const superman = {
defaults: { clark: 'kent' },
hidden: true
};3.3 Use readable synonyms in place of reserved words.
// bad
const superman = {
class: 'alien'
};
// bad
const superman = {
klass: 'alien'
};
// good
const superman = {
type: 'alien'
};Why? They allow you to define all the properties of an object in one place.
```javascript
function getKey(k) {
return `a key named ${k}`;
}
// bad
const obj = {
id: 5,
name: 'San Francisco',
};
obj[getKey('enabled')] = true;
// good
const obj = {
id: 5,
name: 'San Francisco',
[getKey('enabled')]: true,
};
```
3.5 Use object method shorthand.
// bad
const atom = {
value: 1,
addValue: function (value) {
return atom.value + value;
},
};
// good
const atom = {
value: 1,
addValue(value) {
return atom.value + value;
},
};Why? It is shorter to write and descriptive.
```javascript
const lukeSkywalker = 'Luke Skywalker';
// bad
const obj = {
lukeSkywalker: lukeSkywalker
};
// good
const obj = {
lukeSkywalker
};
```
Why? It's easier to tell which properties are using the shorthand.
```javascript
const anakinSkywalker = 'Anakin Skywalker';
const lukeSkywalker = 'Luke Skywalker';
// bad
const obj = {
episodeOne: 1,
twoJedisWalkIntoACantina: 2,
lukeSkywalker,
episodeThree: 3,
mayTheFourth: 4,
anakinSkywalker,
};
// good
const obj = {
lukeSkywalker,
anakinSkywalker,
episodeOne: 1,
twoJedisWalkIntoACantina: 2,
episodeThree: 3,
mayTheFourth: 4,
};
```
4.1 Use the literal syntax for array creation.
// bad const items = new Array(); // good const items = [];
4.2 Use Array#push instead of direct assignment to add items to an array.
const someStack = [];
// bad
someStack[someStack.length] = 'abracadabra';
// good
someStack.push('abracadabra');4.3 Use array spreads ... to copy arrays.
// bad
const len = items.length;
const itemsCopy = [];
let i;
for (i = 0; i < len; i++) {
itemsCopy[i] = items[i];
}
// good
const itemsCopy = [...items];4.4 To convert an array-like object to an array, use Array#from.
const foo = document.querySelectorAll('.foo');
const nodes = Array.from(foo);Why? Destructuring saves you from creating temporary references for those properties.
```javascript
// bad
function getFullName(user) {
const firstName = user.firstName;
const lastName = user.lastName;
return `${firstName} ${lastName}`;
}
// good
function getFullName(obj) {
const { firstName, lastName } = obj;
return `${firstName} ${lastName}`;
}
// best
function getFullName({ firstName, lastName }) {
return `${firstName} ${lastName}`;
}
```
5.2 Use array destructuring.
const arr = [1, 2, 3, 4]; // bad const first = arr[0]; const second = arr[1]; // good const [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
// bad
function processInput(input) {
// then a miracle occurs
return [left, right, top, bottom];
}
// the caller needs to think about the order of return data
const [left, __, top] = processInput(input);
// good
function processInput(input) {
// then a miracle occurs
return { left, right, top, bottom };
}
// the caller selects only the data they need
const { left, right } = processInput(input);
```
6.1 Use single quotes '' for strings.
// bad const name = "Capt. Janeway"; // good const name = 'Capt. Janeway';
6.2 Strings longer than 80 characters should be written across multiple lines using string concatenation.
6.3 Note: If overused, long strings with concatenation could impact performance. jsPerf & Discussion.
// bad const 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.'; // bad const 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.'; // good const 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.';
Why? Template strings give you a readable, concise syntax with proper newlines and string interpolation features.
```javascript
// bad
function sayHi(name) {
return 'How are you, ' + name + '?';
}
// bad
function sayHi(name) {
return ['How are you, ', name, '?'].join();
}
// good
function sayHi(name) {
return `How are you, ${name}?`;
}
```
Why? Function declarations are named, so they're easier to identify in call stacks. Also, the whole body of a function declaration is hoisted, whereas only the reference of a function expression is hoisted. This rule makes it possible to always use Arrow Functions in place of function expressions.
```javascript
// bad
const foo = function () {
};
// good
function foo() {
}
```
7.2 Function expressions:
// immediately-invoked function expression (IIFE)
(() => {
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.
7.4 Note: ECMA-262 defines a block as a list of statements. A function declaration is not a statement. Read ECMA-262's note on this issue.
// bad
if (currentUser) {
function test() {
console.log('Nope.');
}
}
// good
let 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.
// bad
function nope(name, options, arguments) {
// ...stuff...
}
// good
function yup(name, options, args) {
// ...stuff...
}arguments, opt to use rest syntax ... instead.Why?
...is explicit about which arguments you want pulled. Plus rest arguments are a real Array and not Array-like likearguments.
```javascript
// bad
function concatenateAll() {
const args = Array.prototype.slice.call(arguments);
return args.join('');
}
// good
function concatenateAll(...args) {
return args.join('');
}
```
7.7 Use default parameter syntax rather than mutating function arguments.
// really bad
function 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 bad
function handleThings(opts) {
if (opts === void 0) {
opts = {};
}
// ...
}
// good
function handleThings(opts = {}) {
// ...
}7.8 Avoid side effects with default parameters
Why? They are confusing to reason about.
var b = 1;
// bad
function count(a = b++) {
console.log(a);
}
count(); // 1
count(); // 2
count(3); // 3
count(); // 3
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 function declaration.
```javascript
// bad
[1, 2, 3].map(function (x) {
return x * x;
});
// good
[1, 2, 3].map((x) => {
return x * x;
});
```
return statement.Why? Syntactic sugar. It reads well when multiple functions are chained together.
Why not? If you plan on returning an object.
```javascript
// good
[1, 2, 3].map(x => x * x);
// good
[1, 2, 3].reduce((total, n) => {
return total + n;
}, 0);
```
class. Avoid manipulating prototype directly.Why?
classsyntax is more concise and easier to reason about.
```javascript
// bad
function Queue(contents = []) {
this._queue = [...contents];
}
Queue.prototype.pop = function() {
const value = this._queue[0];
this._queue.splice(0, 1);
return value;
}
// good
class Queue {
constructor(contents = []) {
this._queue = [...contents];
}
pop() {
const value = this._queue[0];
this._queue.splice(0, 1);
return value;
}
}
```
extends for inheritance.Why? It is a built-in way to inherit prototype functionality without breaking
instanceof.
```javascript
// bad
const inherits = require('inherits');
function PeekableQueue(contents) {
Queue.apply(this, contents);
}
inherits(PeekableQueue, Queue);
PeekableQueue.prototype.peek = function() {
return this._queue[0];
}
// good
class PeekableQueue extends Queue {
peek() {
return this._queue[0];
}
}
```
9.3 Methods can return this to help with method chaining.
// bad
Jedi.prototype.jump = function() {
this.jumping = true;
return true;
};
Jedi.prototype.setHeight = function(height) {
this.height = height;
};
const luke = new Jedi();
luke.jump(); // => true
luke.setHeight(20); // => undefined
// good
class 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.
class Jedi {
contructor(options = {}) {
this.name = options.name || 'no name';
}
getName() {
return this.name;
}
toString() {
return `Jedi - ${this.getName()}`;
}
}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
// bad
const AirbnbStyleGuide = require('./AirbnbStyleGuide');
module.exports = AirbnbStyleGuide.es6;
// ok
import AirbnbStyleGuide from './AirbnbStyleGuide';
export default AirbnbStyleGuide.es6;
// best
import { es6 } from './AirbnbStyleGuide';
export default es6;
```
Why? This makes sure you have a single default export.
```javascript
// bad
import * as AirbnbStyleGuide from './AirbnbStyleGuide';
// good
import AirbnbStyleGuide from './AirbnbStyleGuide';
```
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.js
export { es6 as default } from './airbnbStyleGuide';
// good
// filename es6.js
import { es6 } from './AirbnbStyleGuide';
export default es6;
```
map() and reduce() instead of loops like for-of.Why? This enforces our immutable rule. Dealing with pure functions that return values is easier to reason about than side-effects.
```javascript
const numbers = [1, 2, 3, 4, 5];
// bad
let sum = 0;
for (let num of numbers) {
sum += num;
}
sum === 15;
// good
let 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;
```
Why? They don't transpile well to ES5.
12.1 Use dot notation when accessing properties.
const luke = {
jedi: true,
age: 28,
};
// bad
const isJedi = luke['jedi'];
// good
const isJedi = luke.jedi;12.2 Use subscript notation [] when accessing properties with a variable.
const luke = {
jedi: true,
age: 28,
};
function getProp(prop) {
return luke[prop];
}
const isJedi = getProp('jedi');13.1 Always use const 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.
// bad superPower = new SuperPower(); // good const superPower = new SuperPower();
13.2 Use one const declaration per variable.
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.
// bad
const items = getItems(),
goSportsTeam = true,
dragonball = 'z';
// bad
// (compare to above, and try to spot the mistake)
const items = getItems(),
goSportsTeam = true;
dragonball = 'z';
// good
const items = getItems();
const goSportsTeam = true;
const dragonball = 'z';13.3 Group all your consts and then group all your lets.
Why? This is helpful when later on you might need to assign a variable depending on one of the previous assigned variables.
```javascript
// bad
let i, len, dragonball,
items = getItems(),
goSportsTeam = true;
// bad
let i;
const items = getItems();
let dragonball;
const goSportsTeam = true;
let len;
// good
const goSportsTeam = true;
const items = getItems();
let dragonball;
let i;
let length;
```
Why?
letandconstare block scoped and not function scoped.
```javascript
// good
function() {
test();
console.log('doing stuff..');
//..other stuff..
const name = getName();
if (name === 'test') {
return false;
}
return name;
}
// bad - unnessary function call
function(hasName) {
const name = getName();
if (!hasName) {
return false;
}
this.setFirstName(name);
return true;
}
// good
function(hasName) {
if (!hasName) {
return false;
}
const name = getName();
this.setFirstName(name);
return true;
}
```
14.1 var declarations get hoisted to the top of their 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.
// 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 let
function 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.
function 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.
function 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.
function example() {
superPower(); // => Flying
function superPower() {
console.log('Flying');
}
}For more information refer to JavaScript Scoping & Hoisting by Ben Cherry.
15.1 Use === and !== over == and !=.
15.2 Conditional statements such as the if statement evaulate their expression using coercion with the ToBoolean abstract method and always follow these simple rules:
'', otherwise trueif ([0]) {
// true
// An array is an object, objects evaluate to true
}15.3 Use shortcuts.
// bad
if (name !== '') {
// ...stuff...
}
// good
if (name) {
// ...stuff...
}
// bad
if (collection.length > 0) {
// ...stuff...
}
// good
if (collection.length) {
// ...stuff...
}15.4 For more information see Truth Equality and JavaScript by Angus Croll.
16.1 Use braces with all multi-line blocks.
// bad
if (test)
return false;
// good
if (test) return false;
// good
if (test) {
return false;
}
// bad
function() { return false; }
// good
function() {
return false;
}16.2 If you're using multi-line blocks with if and else, put else on the same line as your if block's closing brace.
// bad
if (test) {
thing1();
thing2();
}
else {
thing3();
}
// good
if (test) {
thing1();
thing2();
} else {
thing3();
}17.1 Use /** ... */ for multi-line comments. Include a description, specify types and values for all parameters and return values.
// bad
// make() returns a new element
// based on the passed in tag name
//
// @param {String} tag
// @return {Element} element
function make(tag) {
// ...stuff...
return element;
}
// good
/**
* make() returns a new element
* based on the passed in tag name
*
* @param {String} tag
* @return {Element} element
*/
function make(tag) {
// ...stuff...
return element;
}17.2 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.
// bad
const active = true; // is current tab
// good
// is current tab
const active = true;
// bad
function getType() {
console.log('fetching type...');
// set the default type to 'no type'
const type = this._type || 'no type';
return type;
}
// good
function getType() {
console.log('fetching type...');
// set the default type to 'no type'
const type = this._type || 'no type';
return type;
}17.3 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.
17.4 Use // FIXME: to annotate problems.
class Calculator {
constructor() {
// FIXME: shouldn't use a global here
total = 0;
}
}17.5 Use // TODO: to annotate solutions to problems.
class Calculator {
constructor() {
// TODO: total should be configurable by an options param
this.total = 0;
}
}18.1 Use soft tabs set to 2 spaces.
// bad
function() {
∙∙∙∙const name;
}
// bad
function() {
∙const name;
}
// good
function() {
∙∙const name;
}18.2 Place 1 space before the leading brace.
// bad
function test(){
console.log('test');
}
// good
function test() {
console.log('test');
}
// bad
dog.set('attr',{
age: '1 year',
breed: 'Bernese Mountain Dog'
});
// good
dog.set('attr', {
age: '1 year',
breed: 'Bernese Mountain Dog'
});18.3 Place 1 space before the opening parenthesis in control statements (if, while etc.). Place no space before the argument list in function calls and declarations.
// bad
if(isJedi) {
fight ();
}
// good
if (isJedi) {
fight();
}
// bad
function fight () {
console.log ('Swooosh!');
}
// good
function fight() {
console.log('Swooosh!');
}18.4 Set off operators with spaces.
// bad const x=y+5; // good const x = y + 5;
18.5 End files with a single newline character.
// bad
(function(global) {
// ...stuff...
})(this);
// bad
(function(global) {
// ...stuff...
})(this);↵
↵
// good
(function(global) {
// ...stuff...
})(this);↵18.5 Use indentation when making long method chains. Use a leading dot, which emphasizes that the line is a method call, not a new statement.
// 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();
// bad
const leds = stage.selectAll('.led').data(data).enter().append('svg:svg').class('led', true)
.attr('width', (radius + margin) * 2).append('svg:g')
.attr('transform', 'translate(' + (radius + margin) + ',' + (radius + margin) + ')')
.call(tron.led);
// good
const 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);18.6 Leave a blank line after blocks and before the next statement
// bad
if (foo) {
return bar;
}
return baz;
// good
if (foo) {
return bar;
}
return baz;
// bad
const obj = {
foo() {
},
bar() {
},
};
return obj;
// good
const obj = {
foo() {
},
bar() {
},
};
return obj;19.1 Leading commas: Nope.
// bad
const story = [
once
, upon
, aTime
];
// good
const story = [
once,
upon,
aTime,
];
// bad
const hero = {
firstName: 'Ada'
, lastName: 'Lovelace'
, birthYear: 1815
, superPower: 'computers'
};
// good
const hero = {
firstName: 'Ada',
lastName: 'Lovelace',
birthYear: 1815,
superPower: 'computers',
};19.2 Additional trailing comma: Yup.
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 in legacy browsers.
```javascript
// bad - git diff without trailing comma
const hero = {
firstName: 'Florence',
- lastName: 'Nightingale'
+ lastName: 'Nightingale',
+ inventorOf: ['coxcomb graph', 'mordern nursing']
}
// good - git diff with trailing comma
const hero = {
firstName: 'Florence',
lastName: 'Nightingale',
+ inventorOf: ['coxcomb chart', 'mordern nursing'],
}
// bad
const hero = {
firstName: 'Dana',
lastName: 'Scully'
};
const heroes = [
'Batman',
'Superman'
];
// good
const hero = {
firstName: 'Dana',
lastName: 'Scully',
};
const heroes = [
'Batman',
'Superman',
];
```
20.1 Yup.
// bad
(function() {
const name = 'Skywalker'
return name
})()
// good
(() => {
const name = 'Skywalker';
return name;
})();
// good (guards against the function becoming an argument when two files with IIFEs are concatenated)
;(() => {
const name = 'Skywalker';
return name;
})();
21.1 Perform type coercion at the beginning of the statement.
21.2 Strings:
// => this.reviewScore = 9; // bad const totalScore = this.reviewScore + ''; // good const totalScore = String(this.reviewScore);
21.3 Use parseInt for Numbers and always with a radix for type casting.
const inputValue = '4'; // bad const val = new Number(inputValue); // bad const val = +inputValue; // bad const val = inputValue >> 0; // bad const val = parseInt(inputValue); // good const val = Number(inputValue); // good const val = parseInt(inputValue, 10);
21.4 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.
// 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;
21.5 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:
2147483647 >> 0 //=> 2147483647 2147483648 >> 0 //=> -2147483648 2147483649 >> 0 //=> -2147483647
21.6 Booleans:
const age = 0; // bad const hasAge = new Boolean(age); // good const hasAge = Boolean(age); // good const hasAge = !!age;
22.1 Avoid single letter names. Be descriptive with your naming.
// bad
function q() {
// ...stuff...
}
// good
function query() {
// ..stuff..
}22.2 Use camelCase when naming objects, functions, and instances.
// bad
const OBJEcttsssss = {};
const this_is_my_object = {};
function c() {}
// good
const thisIsMyObject = {};
function thisIsMyFunction() {}22.3 Use PascalCase when naming constructors or classes.
// bad
function user(options) {
this.name = options.name;
}
const bad = new user({
name: 'nope',
});
// good
class User {
constructor(options) {
this.name = options.name;
}
}
const good = new User({
name: 'yup',
});22.4 Use a leading underscore _ when naming private properties.
// bad this.__firstName__ = 'Panda'; this.firstName_ = 'Panda'; // good this._firstName = 'Panda';
22.5 Don't save references to this. Use arrow functions or Function#bind.
// bad
function foo() {
const self = this;
return function() {
console.log(self);
};
}
// bad
function foo() {
const that = this;
return function() {
console.log(that);
};
}
// good
function foo() {
return () => {
console.log(this);
};
}22.6 If your file exports a single class, your filename should be exactly the name of the class.
// file contents
class CheckBox {
// ...
}
export default CheckBox;
// in some other file
// bad
import CheckBox from './checkBox';
// bad
import CheckBox from './check_box';
// good
import CheckBox from './CheckBox';22.7 Use camelCase when you export-default a function. Your filename should be identical to your function's name.
function makeStyleGuide() {
}
export default makeStyleGuide;22.8 Use PascalCase when you export a singleton / function library / bare object.
const AirbnbStyleGuide = {
es6: {
}
};
export default AirbnbStyleGuide;23.1 Accessor functions for properties are not required.
23.2 If you do make accessor functions use getVal() and setVal('hello').
// bad dragon.age(); // good dragon.getAge(); // bad dragon.age(25); // good dragon.setAge(25);
23.3 If the property is a boolean, use isVal() or hasVal().
// bad
if (!dragon.age()) {
return false;
}
// good
if (!dragon.hasAge()) {
return false;
}23.4 It's okay to create get() and set() functions, but be consistent.
class Jedi {
constructor(options = {}) {
const lightsaber = options.lightsaber || 'blue';
this.set('lightsaber', lightsaber);
}
set(key, val) {
this[key] = val;
}
get(key) {
return this[key];
}
}24.1 When attaching data payloads to events (whether DOM events or something more proprietary like Backbone events), pass 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:
// bad
$(this).trigger('listingUpdated', listing.id);
...
$(this).on('listingUpdated', function(e, listingId) {
// do something with listingId
});
prefer:
// good
$(this).trigger('listingUpdated', { listingId : listing.id });
...
$(this).on('listingUpdated', function(e, data) {
// do something with data.listingId
});25.1 Prefix jQuery object variables with a $.
// bad
const sidebar = $('.sidebar');
// good
const $sidebar = $('.sidebar');25.2 Cache jQuery lookups.
// bad
function setSidebar() {
$('.sidebar').hide();
// ...stuff...
$('.sidebar').css({
'background-color': 'pink'
});
}
// good
function setSidebar() {
const $sidebar = $('.sidebar');
$sidebar.hide();
// ...stuff...
$sidebar.css({
'background-color': 'pink'
});
}25.3 For DOM queries use Cascading $('.sidebar ul') or parent > child $('.sidebar > ul'). jsPerf
25.4 Use find with scoped jQuery object queries.
// bad
$('ul', '.sidebar').hide();
// bad
$('.sidebar').find('ul').hide();
// good
$('.sidebar ul').hide();
// good
$('.sidebar > ul').hide();
// good
$sidebar.find('ul').hide();27.1 This is a collection of links to the various es6 features.
28.1 Yup.
function() {
return true;
}Learning ES6
Read This
Tools
Other Styleguides
Other Styles
Further Reading
Books
Blogs
Podcasts
This is a list of organizations that are using this style guide. Send us a pull request or open an issue and we'll add you to the list.
This style guide is also available in other languages:
The JavaScript Style Guide Guide Chat With Us About JavaScript(The MIT License)
Copyright (c) 2014 Airbnb
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included 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 OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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