Node.js编码规范 - JavaScript standardStyle() {

Rules

• Use 2 Spaces for indentation.
  eslint: indent

function hello (name) {
  console.log('hi', name)
}

• Use single quotes for strings except to avoid escaping.
  eslint: quotes

console.log('hello there')
$("
")

• No unused variables.
  eslint: no-unused-vars

function myFunction () {
  var result = something();    // ✗ avoid
}

• Add a space after keywords.
  eslint: keyword-spacing

if (condition) { ... }   // ✓ ok
if(condition) { ... }    // ✗ avoid

• Add a space before a function declaration's parentheses.
  eslint: space-before-function-paren

function name (arg) { ... }   // ✓ ok
function name(arg) { ... }    // ✗ avoid

run(function () { ... })      // ✓ ok
run(function() { ... })       // ✗ avoid

• Always use === instead of ==.
  Exception: obj == null is allowed to check for null || undefined.
  esling: eqeqeq

if (name === 'John')   // ✓ ok
if (name == 'John')    // ✗ avoid

if (name !== 'John')   // ✓ ok
if (name != 'John')    // ✗ avoid

• Infix operators must be spaced.
  eslint: space-infix-op

// ✓ ok
var x = 2
var message = 'hello, ' + name + '!'

// ✗ avoid
var x=2
var message = 'hello, '+name+'!'

• Commas should have a space after them.
  eslint: comma-spacing

// ✓ ok
var list = [1, 2, 3, 4]
function greet (name, options) { ... }

// ✗ avoid
var list = [1,2,3,4]
function greet (name,options) { ... }

• Keep else statements on the same line as their curly braces.
  eslint: brace-style

// ✓ ok
if (condition) {
  // ...
} else {
  // ...
}

// ✗ avoid
if (condition) {
  // ...
}
else {
  // ...
}

• For multi-line if statements, use curly braces.
  eslint: curly

// ✓ ok
if (options.quiet !== true) console.log('done')

// ✓ ok
if (options.quiet !== true) {
  console.log('done')
}

// ✗ avoid
if (options.quiet !== true)
  console.log('done')

• Always handle the err function parameter.
  eslint: handle-callback-err

// ✓ ok
run(function (err) {
  if (err) throw err
  window.alert('done')
})

// ✗ avoid
run(function (err) {
  window.alert('done')
})

• Declare browser globals with /* global */ comment.
  Exceptions are: window, document, navigator.
  Prevents accidental use of poorly-named browser globals like open, length, event and name.

/* global alert, prompt */

alert('hi')
prompt('ok?')

Explicitly referencing the function or property on window is okay too, though such code will not run in a Worker which uses self instead of window.
eslint: no-undef

window.alert('hi')   // ✓ ok

• Multiple blank line are not allowed.
  eslint: no-multiple-empty-lines

// ✓ ok
var value = 'hello world'
console.log(value)

// ✗ avoid
var value = 'hello world'


console.log(value)

• For the ternary operator in multi-line setting, place ? and : on their own lines.
  eslint: operator-linebreak

// ✓ ok
var location = env.development ? 'localhost' : 'www.api.com'

// ✓ ok
var location = env.development
  ? 'localhost'
  : 'www.api.com'

// ✗ avoid
var location = env.development ?
  'localhost' :
  'www.api.com'

• For var declarations, write each declaration in its own statements.
  eslint: one-var

// ✓ ok
var silent = true
var verbose = true

// ✗ avoid
var silent = true, verbose = true

// ✗ avoid
var silent = true,
    verbose = true

• Wrap conditional assignments with additional parentheses. This makes it clear that expression is intentionally an assignment (=) rather than a typo for equality (===).
  eslint: no-cond-assign

// ✓ ok
while ((m = text.match(expr))) {
  // ...
}

// ✗ avoid
while (m = text.match(expr)) {
  // ...
}

• Add space in single line blocks.
  eslint: block-spacing

  function foo () {return true}    // ✗ avoid
  function foo () { return true }  // ✓ ok

• Use camelcase when naming variables and functions.
  eslint: camelcase

  function my_function () { }    // ✗ avoid
  function myFunction () { }     // ✓ ok

  var my_var = 'hello'           // ✗ avoid
  var myVar = 'hello'            // ✓ ok

• Tailing commas not allowed.
  eslint: comma-dangle

  var obj = {
    message: 'hello',   // ✗ avoid
  }

• Commas should be placed at the end of the current line.
  eslint: comma-style

  var obj = {
    foo: 'foo'
    ,bar: 'bar'   // ✗ avoid
  }

  var obj = {
    foo: 'foo',
    bar: 'bar'   // ✓ ok
  }

• Dot should be on the same line as property
  eslint: dot-location

  console.
    log('hello')  // ✗ avoid

  console
    .log('hello') // ✓ ok

• Files must be ended with new line.
  eslint: eol-last
• No space between function identifiers and their invocations.
  eslint: func-call-spacing

console.log ('hello') // ✗ avoid
console.log('hello')  // ✓ ok

• Add space between colon and value in key value pairs.
  eslint: key-spacing

var obj = { 'key' : 'value' }    // ✗ avoid
var obj = { 'key' :'value' }     // ✗ avoid
var obj = { 'key':'value' }      // ✗ avoid
var obj = { 'key': 'value' }     // ✓ ok

• Constructor names must begin with a capital letter.
  eslint: new-cap

function animal () {}
var dog = new animal()    // ✗ avoid

function Animal () {}
var dog = new Animal()    // ✓ ok

• Constructor with no arguments must be invoked with parentheses.
  eslint: new-parens

function Animal () {}
var dog = new Animal    // ✗ avoid
var dog = new Animal()  // ✓ ok

• Objects must contain a getter when a setter is defined.
  eslint: accessor-pairs

var person = {
  set name (value) {    // ✗ avoid
    this._name = value
  }
}

var person = {
  set name (value) {
    this._name = value
  },
  get name () {         // ✓ ok
    return this._name
  }
}

• Constructor of derived classes must call super.
  eslint: constructor-super

class Dog {
  constructor () {
    super()   // ✗ avoid
  }
}

class Dog extends Mammal {
  constructor () {
    super()   // ✓ ok
  }
}

• Use array literals instead of array constructors.
  eslint: no-array-constructor

var nums = new Array(1, 2, 3)   // ✗ avoid
var nums = [1, 2, 3]            // ✓ ok

• Avoid using arguments.callee and arguments.caller.
  eslint: no-caller

function foo (n) {
  if (n <= 0) return

  arguments.callee(n - 1)   // ✗ avoid
}

function foo (n) {
  if (n <= 0) return

  foo(n - 1)                // ✓ ok
}

• Avoid modifying variables of class declarations.
  eslint: no-class-assign

class Dog {}
Dog = 'Fido'    // ✗ avoid

• Avoid modifying variables declared using const.
  eslint: no-const-assign

const score = 100
score = 125       // ✗ avoid

• Avoid using constant expressions in conditions (except loops).
  eslint: no-constant-condition

if (false) {    // ✗ avoid
  // ...
}

if (x === 0) {  // ✓ ok
  // ...
}

while (true) {  // ✓ ok
  // ...
}

• No control characters in regular expressions.
  eslint: no-control-regex

var pattern = /\x1f/    // ✗ avoid
var pattern = /\x20/    // ✓ ok

• No debugger statements.
  eslint: no-debugger

function sum (a, b) {
  debugger      // ✗ avoid
  return a + b
}

• No delete operator on variables.
  eslint: no-delete-var

var name
delete name     // ✗ avoid

• No duplicate arguments in function definitions.
  eslint: no-dupe-args

function sum (a, b, a) {  // ✗ avoid
  // ...
}

function sum (a, b, c) {  // ✓ ok
  // ...
}

• No duplicate name in class members.
  eslint: no-dupe-class-members

class Dog {
  bark () {}
  bark () {}    // ✗ avoid
}

• No duplicate keys in object literals.
  eslint: no-dupe-keys

var user = {
  name: 'Jane Doe',
  name: 'John Doe'    // ✗ avoid
}

• No duplicate case labels in switch statements.
  eslint: no-duplicate-case

switch (id) {
  case 1:
    // ...
  case 1:     // ✗ avoid
}

• Use a single import statement per module.
  eslint: no-duplicate-imports

import { myFunc1 } from 'module'
import { myFunc2 } from 'module'          // ✗ avoid

import { myFunc1, myFunc2 } from 'module' // ✓ ok

• No empty character classes in regular expressions.
  eslint: no-empty-character-classes

const myRegex = /^abc[]/      // ✗ avoid
const myRegex = /^abc[a-z]/   // ✓ ok

• No empty destructing patterns.
  eslint: no-empty-patterns

const { a: {} } = foo         // ✗ avoid
const { a: { b } } = foo      // ✓ ok

• No using eval().
  eslint: eval()

eval( "var result = user." + propName ) // ✗ avoid
var result = user[propName]             // ✓ ok

• No reassigning exceptions in catch clauses.
  eslint: no-ex-assign

try {
  // ...
} catch (e) {
  e = 'new value'             // ✗ avoid
}

try {
  // ...
} catch (e) {
  const newVal = 'new value'  // ✓ ok
}

• No extending native objects.
  eslint: no-extend-native

Object.prototype.age = 21     // ✗ avoid

• Avoid unnecessary function binding.
  eslint: no-extra-bind

const name = function () {
  getName()
}.bind(user)    // ✗ avoid

const name = function () {
  this.getName()
}.bind(user)    // ✓ ok

• Avoid unnecessary boolean casts.
  eslint: no-extra-boolean-cast

const result = true
if (!!result) {   // ✗ avoid
  // ...
}

const result = true
if (result) {     // ✓ ok
  // ...
}

• No unnecessary parentheses around function expressions.
  eslint: no-extra-parens

const myFunc = (function () { })   // ✗ avoid
const myFunc = function () { }     // ✓ ok

• Use break to prevent fallthrough in switch cases.
  eslint: no-fallthrough

switch (filter) {
  case 1:
    doSomething()    // ✗ avoid
  case 2:
    doSomethingElse()
}

switch (filter) {
  case 1:
    doSomething()
    break           // ✓ ok
  case 2:
    doSomethingElse()
}

switch (filter) {
  case 1:
    doSomething()
    // fallthrough  // ✓ ok
  case 2:
    doSomethingElse()
}

• No floating decimals.
  eslint: `no-floating-decimal

const discount = .5      // ✗ avoid
const discount = 0.5     // ✓ ok

• Avoid reassigning function declarations.
  eslint: no-func-assign

function myFunc () { }
myFunc = myOtherFunc    // ✗ avoid

• No reassigning read-only global variables.
  eslint: no-global-assign

window = {}     // ✗ avoid

• No impled eval().
  eslint: no-implied-eval

setTimeout("alert('Hello world')")                   // ✗ avoid
setTimeout(function () { alert('Hello world') })     // ✓ ok

• No function declarations in nested blocks.
  eslint: no-inner-declarations

if (authenticated) {
  function setAuthUser () {}    // ✗ avoid
}

• No invalid regular expression strings in RegExp constructors.
  eslint: no-invalid-regexp

RegExp('[a-z')    // ✗ avoid
RegExp('[a-z]')   // ✓ ok

• No irregular whitespace.
  eslint: no-irregular-whitespace

function myFunc () /**/{}   // ✗ avoid

• No using iterator.
  eslint: no-iterator

Foo.prototype.__iterator__ = function () {}   // ✗ avoid

• No labels that share a name with an in scope variable.
  eslint: no-label-var

var score = 100
function game () {
  score: while (true) {      // ✗ avoid
    score -= 10
    if (score > 0) continue score
    break
  }
}

• No label statements.
  eslint: no-labels

label:
  while (true) {
    break label     // ✗ avoid
  }

• No unnecessary nested blocks.
  eslint: no-lone-blocks

function myFunc () {
  {                   // ✗ avoid
    myOtherFunc()
  }
}

function myFunc () {
  myOtherFunc()       // ✓ ok
}

• Avoid mixing spaces and tabs for indentation.
  eslint: no-mixed-spaces-and-tabs
• Do not use multiple spaces except for indentation.
  eslint: no-multi-spaces

const id =    1234    // ✗ avoid
const id = 1234       // ✓ ok

• No multiline strings.
  eslint: no-multi-str

const message = 'Hello \
                 world'     // ✗ avoid

• No new without assigning object to a variable.
  eslint: no-new

new Character()                     // ✗ avoid
const character = new Character()   // ✓ ok

• No using the Function constructor.
  eslint: no-new-func

var sum = new Function('a', 'b', 'return a + b')    // ✗ avoid
```- **No using the `Object` constructor**.
  eslint: `no-new-object`
```javascript
let config = new Object()   // ✗ avoid

• No using new require.
  eslint: no-new-require

const myModule = new require('my-module')    // ✗ avoid

• No using the Symbol constructor.
  eslint: no-new-symbol

const foo = new Symbol('foo')   // ✗ avoid

• No using primitive wrapper instances.
  eslint: no-new-wrappers

const message = new String('hello')   // ✗ avoid

• No calling global object properties as functions.
  eslint: no-obj-calls

const math = Math()   // ✗ avoid

• No octal literals.
  eslint: no-octal

const num = 042     // ✗ avoid
const num = '042'   // ✓ ok

• No octal escape sequences in string literals.
  eslint: no-octal-escape

const copyright = 'Copyright \251'  // ✗ avoid

• Avoid using string concatenation when using __dirname and __filename.
  eslint: no-path-concat

const pathToFile = __dirname + '/app.js'            // ✗ avoid
const pathToFile = path.join(__dirname, 'app.js')   // ✓ ok

• **Avoid using __proto__**. UsegetPrototypeOfinstead. eslint:no-proto`

const foo = obj.__proto__               // ✗ avoid
const foo = Object.getPrototypeOf(obj)  // ✓ ok

• No redeclaring variables.
  eslint: no-redeclare

let name = 'John'
let name = 'Jane'     // ✗ avoid

let name = 'John'
name = 'Jane'         // ✓ ok

• Avoid using multiple spaces in regular expression literals.
  eslint: no-regex-spaces

const regexp = /test   value/   // ✗ avoid

const regexp = /test {3}value/  // ✓ ok
const regexp = /test value/     // ✓ ok

• Assignment in return statements must be surrounded by parentheses.
  eslint: no-return-assign

function sum (a, b) {
  return result = a + b     // ✗ avoid
}

function sum (a, b) {
  return (result = a + b)   // ✓ ok
}

• Avoid assigning a variable to itself.
  eslint: no-self-assign

name = name   // ✗ avoid

• Avoid comparing a variable to itself.
  eslint: no-self-compare

if (score === score) {}   // ✗ avoid

• Avoid using the comma operator.
  eslint: no-sequences

if (doSomething(), !!test) {}   // ✗ avoid

• Restricted names should not be shadowed.
  eslint: no-shadow-restricted-names

let undefined = 'value'     // ✗ avoid

}