Name: javascript
Owner: Meteor
Description: JavaScript Style Guide
Forked from: airbnb/javascript
Created: 2015-06-25 03:11:54.0
Updated: 2017-09-06 23:59:24.0
Pushed: 2017-11-12 14:59:54.0
Homepage: null
Size: 671
Language: JavaScript
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A mostly reasonable approach to JavaScript, with some Meteor flavor
All rules that are automatically linted have the ESLint logo, with a link to the rule, like so: 
This section has been eliminated in the Meteor version, because it does not specify any style rules.
2.1
Use 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.
ad
a = 1;
b = 2;
ood
t a = 1;
t b = 2;
2.2
If you must mutate references, use let instead of var.
Why?
letis block-scoped rather than function-scoped likevar.
ad
count = 1;
true) {
unt += 1;
ood, use the let.
count = 1;
true) {
unt += 1;
2.3 This section removed in the Meteor edition, because it does not specify any style rules.
3.1
Use the literal syntax for object creation.
ad
t item = new Object();
ood
t item = {};
3.2 and 3.3 eliminated in the Meteor edition because Babel can compile reserved words to work fine in old browsers.
3.4 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.
tion getKey(k) {
turn `a key named ${k}`;
ad
t obj = {
: 5,
me: 'San Francisco',
getKey('enabled')] = true;
ood
t obj = {
: 5,
me: 'San Francisco',
etKey('enabled')]: true,
3.5 Use object method shorthand.
ad
t atom = {
lue: 1,
dValue: function (value) {
return atom.value + value;
ood
t atom = {
lue: 1,
dValue(value) {
return atom.value + value;
3.6 Use property value shorthand.
Why? It is shorter to write and descriptive.
t lukeSkywalker = 'Luke Skywalker';
ad
t obj = {
keSkywalker: lukeSkywalker,
ood
t obj = {
keSkywalker,
3.7 Group your shorthand properties at the beginning of your object declaration.
Why? It's easier to tell which properties are using the shorthand.
t anakinSkywalker = 'Anakin Skywalker';
t lukeSkywalker = 'Luke Skywalker';
ad
t obj = {
isodeOne: 1,
oJedisWalkIntoACantina: 2,
keSkywalker,
isodeThree: 3,
yTheFourth: 4,
akinSkywalker,
ood
t obj = {
keSkywalker,
akinSkywalker,
isodeOne: 1,
oJedisWalkIntoACantina: 2,
isodeThree: 3,
yTheFourth: 4,
3.8 Use object spreads ... to copy objects.
ad
t copy = {};
ct.keys(obj).forEach((key) => {
py[key] = obj[key];
ad
t copy = {};
(var key in obj) {
(Object.prototype.hasOwnProperty.call(obj, key)) {
copy[key] = obj[key];
ood
t copy = { ...obj };
4.1
Use the literal syntax for array creation.
ad
t items = new Array();
ood
t items = [];
4.2 Use Array#push instead of direct assignment to add items to an array.
t someStack = [];
ad
Stack[someStack.length] = 'abracadabra';
ood
Stack.push('abracadabra');
4.3 Use array spreads ... to copy arrays.
ad
t len = items.length;
t itemsCopy = [];
i;
(i = 0; i < len; i++) {
emsCopy[i] = items[i];
ood
t itemsCopy = [...items];
4.4 To convert an array-like object to an array, use Array#from.
t foo = document.querySelectorAll('.foo');
t nodes = Array.from(foo);
5.1 Use object destructuring when accessing and using multiple properties of an object.
Why? Destructuring saves you from creating temporary references for those properties.
ad
tion getFullName(user) {
nst firstName = user.firstName;
nst lastName = user.lastName;
turn `${firstName} ${lastName}`;
ood
tion getFullName(obj) {
nst { firstName, lastName } = obj;
turn `${firstName} ${lastName}`;
est
tion getFullName({ firstName, lastName }) {
turn `${firstName} ${lastName}`;
5.2 Use array destructuring.
t arr = [1, 2, 3, 4];
ad
t first = arr[0];
t second = arr[1];
ood
t [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.
ad
tion processInput(input) {
then a miracle occurs
turn [left, right, top, bottom];
he caller needs to think about the order of return data
t [left, __, top] = processInput(input);
ood
tion processInput(input) {
then a miracle occurs
turn { left, right, top, bottom };
he caller selects only the data they need
t { left, right } = processInput(input);
6.1
Use single quotes '' for strings.
ad
t name = "Capt. Janeway";
ood
t name = 'Capt. Janeway';
6.2
Single-line strings longer than 80 characters should be written across multiple lines using string concatenation. If you are writing a multiline string, use template strings as in 6.4. This is a change in the Meteor edition. Note: If overused, long strings with concatenation could impact performance. jsPerf & Discussion.
ad
t 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.';
ad
t errorMessage = 'This is a super long error that was thrown because \
atman. When you stop to think about how Batman had anything to do \
this, you would get nowhere \
.';
ood
t errorMessage = 'This is a super long error that was thrown because ' +
f Batman. When you stop to think about how Batman had anything to do ' +
ith this, you would get nowhere fast.';
6.3 This non-rule merged as a note into the previous rule in the Meteor edition.
6.4 When programmatically building up strings, use template strings instead of concatenation.
Why? Template strings give you a readable, concise syntax with proper newlines and string interpolation features.
ad
tion sayHi(name) {
turn 'How are you, ' + name + '?';
ad
tion sayHi(name) {
turn ['How are you, ', name, '?'].join();
ood
tion sayHi(name) {
turn `How are you, ${name}?`;
7.1
Use function declarations instead of function expressions.
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.
ad
t foo = function () {
ood
tion foo() {
7.2 Removed in the Meteor edition.
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. This note merged into the previous rule in the Meteor edition.
ad
currentUser) {
nction test() {
console.log('Nope.');
ood
test;
currentUser) {
st = () => {
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.
ad
tion nope(name, options, arguments) {
...stuff...
ood
tion yup(name, options, args) {
...stuff...
7.6 Never use 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.
ad
tion concatenateAll() {
nst args = Array.prototype.slice.call(arguments);
turn args.join('');
ood
tion concatenateAll(...args) {
turn args.join('');
7.7 Use default parameter syntax rather than mutating function arguments.
eally bad
tion 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.
ts = opts || {};
...
till bad
tion handleThings(opts) {
(opts === void 0) {
opts = {};
...
ood
tion handleThings(opts = {}) {
...
7.8 Avoid side effects with default parameters
Why? They are confusing to reason about.
b = 1;
ad
tion count(a = b++) {
ole.log(a);
t(); // 1
t(); // 2
t(3); // 3
t(); // 3
7.9 Use argument spreads to interpolate arguments in function calls.
t prefix = [a, b];
t suffix = [c, d, e];
ad
ix.push.apply(prefix, suffix);
ood
ix.push(...suffix);
ad
Function.apply(null, prefix.concat(suffix));
ood
Function(...prefix, ...suffix);
The exception to this advice is when you really need to use a
different, non-null value of this. Then .apply (or .call) is
probably a better option.
The same goes for new expressions.
s A {
nstructor(...args) { ... }
eally bad
t instance = Object.create(A.prototype);
ototype.constructor.apply(instance, prefix.concat(suffix));
ood
t instance = new A(...prefix, ...suffix);
8.1 When you must use function expressions (as when passing an anonymous function), use arrow function notation.
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.
ad
2, 3].map(function (x) {
turn x * x;
ood
2, 3].map((x) => {
turn x * x;
8.2 If the function body fits on one line and there is only a single argument, feel free to omit the braces and parentheses, and use the implicit return. Otherwise, add the parentheses, braces, and use a return statement.
Why? Syntactic sugar. It reads well when multiple functions are chained together.
Why not? If you plan on returning an object.
ood
2, 3].map(x => x * x);
ood
2, 3].reduce((total, n) => {
turn total + n;
);
9.1 Always use class. Avoid manipulating prototype directly.
Why?
classsyntax is more concise and easier to reason about.
ad
tion Queue(contents = []) {
is._queue = [...contents];
e.prototype.pop = function() {
nst value = this._queue[0];
is._queue.splice(0, 1);
turn value;
ood
s Queue {
nstructor(contents = []) {
this._queue = [...contents];
p() {
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.
ad
t inherits = require('inherits');
tion PeekableQueue(contents) {
eue.apply(this, contents);
rits(PeekableQueue, Queue);
ableQueue.prototype.peek = function() {
turn this._queue[0];
ood
s PeekableQueue extends Queue {
ek() {
return this._queue[0];
9.3 Methods can return this to help with method chaining.
ad
.prototype.jump = function() {
is.jumping = true;
turn true;
.prototype.setHeight = function(height) {
is.height = height;
t luke = new Jedi();
.jump(); // => true
.setHeight(20); // => undefined
ood
s Jedi {
mp() {
this.jumping = true;
return this;
tHeight(height) {
this.height = height;
return this;
t luke = new Jedi();
.jump()
etHeight(20);
9.4 It's okay to write a custom toString() method, just make sure it works successfully and causes no side effects.
s Jedi {
ntructor(options = {}) {
this.name = options.name || 'no name';
tName() {
return this.name;
String() {
return `Jedi - ${this.getName()}`;
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.
ad
t AirbnbStyleGuide = require('./AirbnbStyleGuide');
le.exports = AirbnbStyleGuide.es6;
k
rt AirbnbStyleGuide from './AirbnbStyleGuide';
rt default AirbnbStyleGuide.es6;
est
rt { es6 } from './AirbnbStyleGuide';
rt default es6;
10.2 Do not use wildcard imports.
Why? This makes sure you have a single default export.
ad
rt * as AirbnbStyleGuide from './AirbnbStyleGuide';
ood
rt 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.
ad
ilename es6.js
rt { es6 as default } from './airbnbStyleGuide';
ood
ilename es6.js
rt { es6 } from './AirbnbStyleGuide';
rt default es6;
11.1 Don't use iterators. Prefer JavaScript's higher-order functions like 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.
t numbers = [1, 2, 3, 4, 5];
ad
sum = 0;
(let num of numbers) {
m += num;
=== 15;
ood
sum = 0;
ers.forEach((num) => sum += num);
=== 15;
est (use the functional force)
t sum = numbers.reduce((total, num) => total + num, 0);
=== 15;
11.2 Don't use generators for now.
Why? They don't transpile well to ES5.
12.1 Use dot notation when accessing properties.
t luke = {
di: true,
e: 28,
ad
t isJedi = luke['jedi'];
ood
t isJedi = luke.jedi;
12.2 Use subscript notation [] when accessing properties with a variable.
t luke = {
di: true,
e: 28,
tion getProp(prop) {
turn luke[prop];
t 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.
ad
rPower = new SuperPower();
ood
t 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.
ad
t items = getItems(),
goSportsTeam = true,
dragonball = 'z';
ad
compare to above, and try to spot the mistake)
t items = getItems(),
goSportsTeam = true;
dragonball = 'z';
ood
t items = getItems();
t goSportsTeam = true;
t 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.
ad
i, len, dragonball,
items = getItems(),
goSportsTeam = true;
ad
i;
t items = getItems();
dragonball;
t goSportsTeam = true;
len;
ood
t goSportsTeam = true;
t items = getItems();
dragonball;
i;
length;
13.4 Assign variables where you need them, but place them in a reasonable place.
Why?
letandconstare block scoped and not function scoped.
ood
tion() {
st();
nsole.log('doing stuff..');
..other stuff..
nst name = getName();
(name === 'test') {
return false;
turn name;
ad - unnessary function call
tion(hasName) {
nst name = getName();
(!hasName) {
return false;
is.setFirstName(name);
turn true;
ood
tion(hasName) {
(!hasName) {
return false;
nst name = getName();
is.setFirstName(name);
turn true;
14.1 14.2 14.3 14.4 Non-rules removed in the Meteor edition.
For more information refer to [JavaScript Scoping & Hoisting](http://www.adequatelygood.com/2010/2/JavaS cript-Scoping-and-Hoisting) by Ben Cherry.
15.1 Use === and !== over == and !=.
15.2/15.3/15.4
Use shortcuts. Note: Conditional statements such as the if statement evaluate their expression using coercion with the ToBoolean abstract method and always follow the simple rules below. For more information see Truth Equality and JavaScript by Angus Croll. (15.2, 15.3, and 15.4 merged in Meteor edition):
'', otherwise truead
name !== '') {
...stuff...
ood
name) {
...stuff...
ad
collection.length > 0) {
...stuff...
ood
collection.length) {
...stuff...
ote
[0]) {
true
An array is an object, objects evaluate to true
16.1
Use braces with all multi-line blocks.
ad
test)
turn false;
ood
test) return false;
ood
test) {
turn false;
ad
tion() { return false; }
ood
tion() {
turn 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.
ad
test) {
ing1();
ing2();
{
ing3();
ood
test) {
ing1();
ing2();
se {
ing3();
17.1 Use /** ... */ for method doc comments. Include a description, specify types and values for all parameters and return values. In the Meteor edition, this rule has been updated to only refer to doc comments.
ad
ake() returns a new element
ased on the passed in tag name
param {String} tag
return {Element} element
tion make(tag) {
...stuff...
turn element;
ood
ake() returns a new element
ased on the passed in tag name
param {String} tag
return {Element} element
tion make(tag) {
...stuff...
turn element;
17.2 Use // for all other comments. Place single line comments on a newline above the subject of the comment. Put an empty line before the comment. Has been updated in Meteor edition to refer to all non-doc comments.
ad
t active = true; // is current tab
ood
s current tab
t active = true;
ad
tion getType() {
nsole.log('fetching type...');
set the default type to 'no type'
nst type = this._type || 'no type';
turn type;
ood
tion getType() {
nsole.log('fetching type...');
set the default type to 'no type'
nst type = this._type || 'no type';
turn 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.
s Calculator {
nstructor() {
// FIXME: shouldn't use a global here
total = 0;
17.5 Use // TODO: to annotate solutions to problems.
s Calculator {
nstructor() {
// TODO: total should be configurable by an options param
this.total = 0;
18.1
Use soft tabs set to 2 spaces.
ad
tion() {
const name;
ad
tion() {
st name;
ood
tion() {
nst name;
18.2
Place 1 space before the leading brace.
ad
tion test(){
nsole.log('test');
ood
tion test() {
nsole.log('test');
ad
set('attr',{
e: '1 year',
eed: 'Bernese Mountain Dog',
ood
set('attr', {
e: '1 year',
eed: '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.
ad
sJedi) {
ght ();
ood
isJedi) {
ght();
ad
tion fight () {
nsole.log ('Swooosh!');
ood
tion fight() {
nsole.log('Swooosh!');
18.4
Set off operators with spaces.
ad
t x=y+5;
ood
t x = y + 5;
18.5 End files with a single newline character.
ad
ction(global) {
...stuff...
his);
avascript
ad
ction(global) {
...stuff...
his);?
avascript
ood
ction(global) {
...stuff...
his);?
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.
ad
items').find('.selected').highlight().end().find('.open').updateCount();
ad
items').
nd('.selected').
highlight().
end().
nd('.open').
updateCount();
ood
items')
ind('.selected')
.highlight()
.end()
ind('.open')
.updateCount();
ad
t 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);
ood
t leds = stage.selectAll('.led')
.data(data)
nter().append('svg:svg')
.classed('led', true)
.attr('width', (radius + margin) * 2)
ppend('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.
ad
foo) {
turn bar;
rn baz;
ood
foo) {
turn bar;
rn baz;
ad
t obj = {
o() {
r() {
rn obj;
ood
t obj = {
o() {
r() {
rn obj;
19.1
Leading commas: Nope.
ad
t story = [
once
upon
aTime
ood
t story = [
ce,
on,
ime,
ad
t hero = {
firstName: 'Ada'
lastName: 'Lovelace'
birthYear: 1815
superPower: 'computers'
ood
t hero = {
rstName: 'Ada',
stName: 'Lovelace',
rthYear: 1815,
perPower: '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.
ad - git diff without trailing comma
t hero = {
firstName: 'Florence',
lastName: 'Nightingale'
lastName: 'Nightingale',
inventorOf: ['coxcomb graph', 'mordern nursing']
ood - git diff with trailing comma
t hero = {
firstName: 'Florence',
lastName: 'Nightingale',
inventorOf: ['coxcomb chart', 'mordern nursing'],
ad
t hero = {
rstName: 'Dana',
stName: 'Scully'
t heroes = [
atman',
uperman'
ood
t hero = {
rstName: 'Dana',
stName: 'Scully',
t heroes = [
atman',
uperman',
20.1
Yup.
ad
ction() {
nst name = 'Skywalker'
turn name
ood
=> {
nst name = 'Skywalker';
turn name;
;
ood (guards against the function becoming an argument when two files with IIFEs are concatenated)
=> {
nst name = 'Skywalker';
turn name;
;
21.1 Perform type coercion at the beginning of the statement.
21.2 Strings:
=> this.reviewScore = 9;
ad
t totalScore = this.reviewScore + '';
ood
t totalScore = String(this.reviewScore);
21.3
Use parseInt to convert strings to numbers, and always with a radix argument.
t inputValue = '4';
ad
t val = new Number(inputValue);
ad
t val = inputValue >> 0;
ad
t val = parseInt(inputValue);
ood
t val = parseInt(inputValue, 10);
Use the Number constructor (without new) to coerce values that are
not strings to numbers, as in Number(new Date) + 1000. The unary +
operator is an acceptable shorthand for Number(...), but only if the
expression is not involved in a larger expression, as in +new Date.
Note that the Number constructor will return NaN if the value
cannot be converted to a number, including when the value is
undefined. If the output might be NaN (likely because the input
might be undefined), be sure to test for that possibility after
attempting the conversion:
val = Number(inputValue);
isNaN(val)) {
l = 0;
Better yet, avoid the possibility of NaN through other means, such
as providing default values for optional function parameters.
21.4 If you have a very good reason for using some other kind of coercion technique, be it for performance or because you need a very specific output behavior, then you should absolutely leave a comment justifying your choice.
ood
arseInt was the reason my code was slow.
itshifting the String to coerce it to a
umber made it a lot faster.
t val = inputValue >> 0;
ood
ruthy inputs must always be coerced to 1, and falsy inputs must
lways be cocerced to 0.
t zeroOrOne = inputValue ? 1 : 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:
483647 >> 0 //=> 2147483647
483648 >> 0 //=> -2147483648
483649 >> 0 //=> -2147483647
21.6 Booleans:
t age = 0;
ad
t hasAge = new Boolean(age);
ood
t hasAge = Boolean(age);
ood
t hasAge = !!age;
22.1 Avoid single letter names. Be descriptive with your naming.
ad
tion q() {
...stuff...
ood
tion query() {
..stuff..
22.2
Use camelCase when naming objects, functions, and instances.
ad
t OBJEcttsssss = {};
t this_is_my_object = {};
tion c() {}
ood
t thisIsMyObject = {};
tion thisIsMyFunction() {}
22.3 Use PascalCase when naming constructors or classes.
ad
tion user(options) {
is.name = options.name;
t bad = new user({
me: 'nope',
ood
s User {
nstructor(options) {
this.name = options.name;
t good = new User({
me: 'yup',
22.4 Use a leading underscore _ when naming private properties.
ad
.__firstName__ = 'Panda';
.firstName_ = 'Panda';
ood
._firstName = 'Panda';
22.5 Don't save references to this. Use arrow functions or Function#bind.
ad
tion foo() {
nst self = this;
turn function() {
console.log(self);
ad
tion foo() {
nst that = this;
turn function() {
console.log(that);
ood
tion foo() {
turn () => {
console.log(this);
22.6 If your file exports a single class, your filename should be exactly the name of the class.
ile contents
rt default class CheckBox {
...
n some other file
ad
rt CheckBox from './checkBox';
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rt CheckBox from './check_box';
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rt CheckBox from './CheckBox';
22.7 Use camelCase when you export-default a function. Your filename should be identical to your function's name.
tion makeStyleGuide() {
rt default makeStyleGuide;
22.8 Use PascalCase when you export a singleton / function library / bare object.
t AirbnbStyleGuide = {
6: {
rt default AirbnbStyleGuide;
22.9 Prefer exporting declarations
where they are declared, rather than at the end of the file:
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tion createUser(name) { ... }
tion getOrCreateUser(name) { ... }
.. rest of file ...
rt {
eateUser,
tOrCreateUser,
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rt function createUser(name) { ... }
rt function getOrCreateUser(name) { ... }
.. rest of file ...
This style ensures that the set of exports remains up-to-date as
declarations are added or removed.
23.1 Accessor functions for properties are not required.
23.2 If you do make accessor functions use getVal() and setVal('hello').
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on.age();
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on.getAge();
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on.age(25);
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on.setAge(25);
23.3 If the property is a boolean, use isVal() or hasVal().
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!dragon.age()) {
turn false;
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!dragon.hasAge()) {
turn false;
23.4 It's okay to create get() and set() functions, but be consistent.
s Jedi {
nstructor(options = {}) {
const lightsaber = options.lightsaber || 'blue';
this.set('lightsaber', lightsaber);
t(key, val) {
this[key] = val;
t(key) {
return this[key];
23.5 Strongly prefer accessor methods to defining ES5 getter and setter properties:
s Jedi {
nstructor({ lightsaber = blue }) {
this._lightsaber = lightsaber;
bad; use a normal getter method instead
t lightsaber() {
return this._lightsaber;
bad; use a normal setter method instead
t lightsaber(newLightSaber) {
return this._lightsaber = newLightSaber;
Not only is this style rarely more readable than the method equivalent, performance can suffer dramatically when code relies on specially-defined properties rather than just using normal properties.
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:
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is).trigger('listingUpdated', listing.id);
is).on('listingUpdated', function(e, listingId) {
do something with listingId
prefer:
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is).trigger('listingUpdated', { listingId : listing.id });
is).on('listingUpdated', function(e, data) {
do something with data.listingId
25.1 Prefix jQuery object variables with a $.
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t sidebar = $('.sidebar');
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t $sidebar = $('.sidebar');
25.2 Cache jQuery lookups.
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tion setSidebar() {
'.sidebar').hide();
...stuff...
'.sidebar').css({
'background-color': 'pink'
;
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tion setSidebar() {
nst $sidebar = $('.sidebar');
idebar.hide();
...stuff...
idebar.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.
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l', '.sidebar').hide();
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sidebar').find('ul').hide();
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sidebar ul').hide();
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sidebar > ul').hide();
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ebar.find('ul').hide();
27.1 This is a collection of links to the various es6 features.
(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.