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standard 规则列表,太多不必阅读。
了解 standard
的最好方式是安装它,然后写代码尝试。
eslint: indent
function hello (name) {
console.log('hi', name)
}
eslint: quotes
console.log('hello there')
$("<div class='box'>")
eslint: no-unused-vars
function myFunction () {
var result = something() // ✗ avoid
}
eslint: keyword-spacing
if (condition) { ... } // ✓ ok
if(condition) { ... } // ✗ avoid
eslint: space-before-function-paren
function name (arg) { ... } // ✓ ok
function name(arg) { ... } // ✗ avoid
run(function () { ... }) // ✓ ok
run(function() { ... }) // ✗ avoid
===
不使用 ==
。obj == null
检测 null || undefined
。eslint: eqeqeq
if (name === 'John') // ✓ ok
if (name == 'John') // ✗ avoid
if (name !== 'John') // ✓ ok
if (name != 'John') // ✗ avoid
eslint: space-infix-ops
// ✓ ok
var x = 2
var message = 'hello, ' + name + '!'
// ✗ avoid
var x=2
var message = 'hello, '+name+'!'
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) { ... }
else
与它的大括号同行。eslint: brace-style
// ✓ ok
if (condition) {
// ...
} else {
// ...
}
// ✗ avoid
if (condition) {
// ...
}
else {
// ...
}
if
语句如果包含多个语句则使用大括号。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')
err
参数。eslint: handle-callback-err
// ✓ ok
run(function (err) {
if (err) throw err
window.alert('done')
})
// ✗ avoid
run(function (err) {
window.alert('done')
})
window.
。document
, console
和 navigator
。eslint: no-undef
window.alert('hi') // ✓ ok
eslint: no-multiple-empty-lines
// ✓ ok
var value = 'hello world'
console.log(value)
// ✗ avoid
var value = 'hello world'
console.log(value)
?
和 :
放在各自的行上。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'
var
声明,每个声明占一行。eslint: one-var
// ✓ ok
var silent = true
var verbose = true
// ✗ avoid
var silent = true, verbose = true
// ✗ avoid
var silent = true,
verbose = true
=
),而不是一个等式 (===
) 的误写。eslint: no-cond-assign
// ✓ ok
while ((m = text.match(expr))) {
// ...
}
// ✗ avoid
while (m = text.match(expr)) {
// ...
}
eslint: block-spacing
function foo () {return true} // ✗ avoid
function foo () { return true } // ✓ ok
eslint: camelcase
function my_function () { } // ✗ avoid
function myFunction () { } // ✓ ok
var my_var = 'hello' // ✗ avoid
var myVar = 'hello' // ✓ ok
eslint: comma-dangle
var obj = {
message: 'hello', // ✗ avoid
}
eslint: comma-style
var obj = {
foo: 'foo'
,bar: 'bar' // ✗ avoid
}
var obj = {
foo: 'foo',
bar: 'bar' // ✓ ok
}
.
应当与属性同行。eslint: dot-location
console.
log('hello') // ✗ avoid
console
.log('hello') // ✓ ok
elint: eol-last
eslint: func-call-spacing
console.log ('hello') // ✗ avoid
console.log('hello') // ✓ ok
eslint: key-spacing
var obj = { 'key' : 'value' } // ✗ avoid
var obj = { 'key' :'value' } // ✗ avoid
var obj = { 'key':'value' } // ✗ avoid
var obj = { 'key': 'value' } // ✓ ok
eslint: new-cap
function animal () {}
var dog = new animal() // ✗ avoid
function Animal () {}
var dog = new Animal() // ✓ ok
eslint: new-parens
function Animal () {}
var dog = new Animal // ✗ avoid
var dog = new Animal() // ✓ ok
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
}
}
super
。eslint: constructor-super
class Dog {
constructor () {
super() // ✗ avoid
}
}
class Dog extends Mammal {
constructor () {
super() // ✓ ok
}
}
eslint: no-array-constructor
var nums = new Array(1, 2, 3) // ✗ avoid
var nums = [1, 2, 3] // ✓ ok
arguments.callee
和 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)
}
eslint: no-class-assign
class Dog {}
Dog = 'Fido' // ✗ avoid
const
声明的变量。eslint: no-const-assign
const score = 100
score = 125 // ✗ avoid
eslint: no-constant-condition
if (false) { // ✗ avoid
// ...
}
if (x === 0) { // ✓ ok
// ...
}
while (true) { // ✓ ok
// ...
}
eslint: no-control-regex
var pattern = /\x1f/ // ✗ avoid
var pattern = /\x20/ // ✓ ok
debugger
语句。eslint: no-debugger
function sum (a, b) {
debugger // ✗ avoid
return a + b
}
delete
操作符。eslint: no-delete-var
var name
delete name // ✗ avoid
eslint: no-dupe-args
function sum (a, b, a) { // ✗ avoid
// ...
}
function sum (a, b, c) { // ✓ ok
// ...
}
eslint: no-dupe-class-members
class Dog {
bark () {}
bark () {} // ✗ avoid
}
eslint: no-dupe-keys
var user = {
name: 'Jane Doe',
name: 'John Doe' // ✗ avoid
}
switch
语句无重复 case
从句。eslint: no-duplicate-case
switch (id) {
case 1:
// ...
case 1: // ✗ avoid
}
eslint: no-duplicate-imports
import { myFunc1 } from 'module'
import { myFunc2 } from 'module' // ✗ avoid
import { myFunc1, myFunc2 } from 'module' // ✓ ok
eslint: no-empty-character-class
const myRegex = /^abc[]/ // ✗ avoid
const myRegex = /^abc[a-z]/ // ✓ ok
eslint: no-empty-pattern
const { a: {} } = foo // ✗ avoid
const { a: { b } } = foo // ✓ ok
eval()
。eslint: no-eval
eval( "var result = user." + propName ) // ✗ avoid
var result = user[propName] // ✓ ok
catch
语句中不要对错误对象重新赋值。eslint: no-ex-assign
try {
// ...
} catch (e) {
e = 'new value' // ✗ avoid
}
try {
// ...
} catch (e) {
const newVal = 'new value' // ✓ ok
}
eslint: no-extend-native
Object.prototype.age = 21 // ✗ avoid
.bind()
。eslint: no-extra-bind
const name = function () {
getName()
}.bind(user) // ✗ avoid
const name = function () {
this.getName()
}.bind(user) // ✓ ok
eslint: no-extra-boolean-cast
const result = true
if (!!result) { // ✗ avoid
// ...
}
const result = true
if (result) { // ✓ ok
// ...
}
eslint: no-extra-parens
const myFunc = (function () { }) // ✗ avoid
const myFunc = function () { } // ✓ ok
switch
语句使用 break
,避免运行到下一个 case
。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()
}
eslint: no-floating-decimal
const discount = .5 // ✗ avoid
const discount = 0.5 // ✓ ok
eslint: no-func-assign
function myFunc () { }
myFunc = myOtherFunc // ✗ avoid
eslint: no-global-assign
window = {} // ✗ avoid
eval()
。eslint: no-implied-eval
setTimeout("alert('Hello world')") // ✗ avoid
setTimeout(function () { alert('Hello world') }) // ✓ ok
eslint: no-inner-declarations
if (authenticated) {
function setAuthUser () {} // ✗ avoid
}
RegExp
构造器不使用非法的正则表达式字符串。eslint: no-invalid-regexp
RegExp('[a-z') // ✗ avoid
RegExp('[a-z]') // ✓ ok
eslint: no-irregular-whitespace
function myFunc () /*<NBSP>*/{} // ✗ avoid
__iterator__
。eslint: no-iterator
Foo.prototype.__iterator__ = function () {} // ✗ avoid
eslint: no-label-var
var score = 100
function game () {
score: 50 // ✗ avoid
}
eslint: no-labels
label:
while (true) {
break label // ✗ avoid
}
eslint: no-lone-blocks
function myFunc () {
{ // ✗ avoid
myOtherFunc()
}
}
function myFunc () {
myOtherFunc() // ✓ ok
}
eslint: no-mixed-spaces-and-tabs
eslint: no-multi-spaces
const id = 1234 // ✗ avoid
const id = 1234 // ✓ ok
eslint: no-multi-str
const message = 'Hello \
world' // ✗ avoid
new
。eslint: no-new
new Character() // ✗ avoid
const character = new Character() // ✓ ok
Function
构造器。eslint: no-new-func
var sum = new Function('a', 'b', 'return a + b') // ✗ avoid
Object
构造器。eslint: no-new-object
let config = new Object() // ✗ avoid
new require
。eslint: no-new-require
const myModule = new require('my-module') // ✗ avoid
Symbol
构造器。eslint: no-new-symbol
const foo = new Symbol('foo') // ✗ avoid
eslint: no-new-wrappers
const message = new String('hello') // ✗ avoid
eslint: no-obj-calls
const math = Math() // ✗ avoid
eslint: no-octal
const num = 042 // ✗ avoid
const num = '042' // ✓ ok
eslint: no-octal-escape
const copyright = 'Copyright \251' // ✗ avoid
__dirname
和 __filename
不用于字符串拼接。eslint: no-path-concat
const pathToFile = __dirname + '/app.js' // ✗ avoid
const pathToFile = path.join(__dirname, 'app.js') // ✓ ok
__proto__
,应使用 getPrototypeOf
。eslint: no-proto
const foo = obj.__proto__ // ✗ avoid
const foo = Object.getPrototypeOf(obj) // ✓ ok
eslint: no-redeclare
let name = 'John'
let name = 'Jane' // ✗ avoid
let name = 'John'
name = 'Jane' // ✓ ok
eslint: no-regex-spaces
const regexp = /test value/ // ✗ avoid
const regexp = /test {3}value/ // ✓ ok
const regexp = /test value/ // ✓ ok
eslint: no-return-assign
function sum (a, b) {
return result = a + b // ✗ avoid
}
function sum (a, b) {
return (result = a + b) // ✓ ok
}
eslint: no-self-assign
name = name // ✗ avoid
esint: no-self-compare
if (score === score) {} // ✗ avoid
eslint: no-sequences
if (doSomething(), !!test) {} // ✗ avoid
eslint: no-shadow-restricted-names
let undefined = 'value' // ✗ avoid
eslint: no-sparse-arrays
let fruits = ['apple',, 'orange'] // ✗ avoid
eslint: no-tabs
eslint: no-template-curly-in-string
const message = 'Hello ${name}' // ✗ avoid
const message = `Hello ${name}` // ✓ ok
super()
必须在访问 this
之前调用。eslint: no-this-before-super
class Dog extends Animal {
constructor () {
this.legs = 4 // ✗ avoid
super()
}
}
throw
应当抛出一个 Error
对象。eslint: no-throw-literal
throw 'error' // ✗ avoid
throw new Error('error') // ✓ ok
eslint: no-trailing-spaces
undefined
。eslint: no-undef-init
let name = undefined // ✗ avoid
let name
name = 'value' // ✓ ok
eslint: no-unmodified-loop-condition
for (let i = 0; i < items.length; j++) {...} // ✗ avoid
for (let i = 0; i < items.length; i++) {...} // ✓ ok
eslint: no-unneeded-ternary
let score = val ? val : 0 // ✗ avoid
let score = val || 0 // ✓ ok
return
, throw
, continue
, break
语句后面不要有代码。eslint: no-unreachable
function doSomething () {
return true
console.log('never called') // ✗ avoid
}
finally
语句块无流程控制语句。eslint: no-unsafe-finally
try {
// ...
} catch (e) {
// ...
} finally {
return 42 // ✗ avoid
}
in
操作符的左操作数不要使用 !
。eslint: no-unsafe-negation
if (!key in obj) {} // ✗ avoid
.call()
和 .apply()
。eslint: no-useless-call
sum.call(null, 1, 2, 3) // ✗ avoid
eslint: no-useless-computed-key
const user = { ['name']: 'John Doe' } // ✗ avoid
const user = { name: 'John Doe' } // ✓ ok
eslint: no-useless-constructor
class Car {
constructor () { // ✗ avoid
}
}
eslint: no-useless-escape
let message = 'Hell\o' // ✗ avoid
eslint: no-useless-rename
import { config as config } from './config' // ✗ avoid
import { config } from './config' // ✓ ok
eslint: no-whitespace-before-property
user .name // ✗ avoid
user.name // ✓ ok
with
语句。eslint: no-with
with (val) {...} // ✗ avoid
eslint: object-property-newline
const user = {
name: 'Jane Doe', age: 30,
username: 'jdoe86' // ✗ avoid
}
const user = { name: 'Jane Doe', age: 30, username: 'jdoe86' } // ✓ ok
const user = {
name: 'Jane Doe',
age: 30,
username: 'jdoe86'
} // ✓ ok
eslint: padded-blocks
if (user) {
// ✗ avoid
const name = getName()
}
if (user) {
const name = getName() // ✓ ok
}
eslint: rest-spread-spacing
fn(... args) // ✗ avoid
fn(...args) // ✓ ok
eslint: semi-spacing
for (let i = 0 ;i < items.length ;i++) {...} // ✗ avoid
for (let i = 0; i < items.length; i++) {...} // ✓ ok
eslint: space-before-blocks
if (admin){...} // ✗ avoid
if (admin) {...} // ✓ ok
eslint: space-in-parens
getName( name ) // ✗ avoid
getName(name) // ✓ ok
eslint: space-unary-ops
typeof!admin // ✗ avoid
typeof !admin // ✓ ok
eslint: spaced-comment
//comment // ✗ avoid
// comment // ✓ ok
/*comment*/ // ✗ avoid
/* comment */ // ✓ ok
eslint: template-curly-spacing
const message = `Hello, ${ name }` // ✗ avoid
const message = `Hello, ${name}` // ✓ ok
isNaN()
检查 NaN
。eslint: use-isnan
if (price === NaN) { } // ✗ avoid
if (isNaN(price)) { } // ✓ ok
typeof
必须跟合法的字符串比较。eslint: valid-typeof
typeof name === 'undefimed' // ✗ avoid
typeof name === 'undefined' // ✓ ok
eslint: wrap-iife
const getName = function () { }() // ✗ avoid
const getName = (function () { }()) // ✓ ok
const getName = (function () { })() // ✓ ok
yield*
的 *
前后要有一个空格。eslint: yield-star-spacing
yield* increment() // ✗ avoid
yield * increment() // ✓ ok
eslint: yoda
if (42 === age) { } // ✗ avoid
if (age === 42) { } // ✓ ok
eslint: semi
window.alert('hi') // ✓ ok
window.alert('hi'); // ✗ avoid
(
, [
, “` 开始行。这是省略分号时唯一的陷阱。standard 会保护你不落入陷阱。eslint: no-unexpected-multiline
// ✓ ok
;(function () {
window.alert('ok')
}())
// ✗ avoid
(function () {
window.alert('ok')
}())
// ✓ ok
;[1, 2, 3].forEach(bar)
// ✗ avoid
[1, 2, 3].forEach(bar)
// ✓ ok
;`hello`.indexOf('o')
// ✗ avoid
`hello`.indexOf('o')
提示:如果你经常这样写代码,你可能是过于聪明了。
不鼓励过于聪明的简写,表达式应尽可能清晰且容易阅读:
不要这样:
;[1, 2, 3].forEach(bar)
这样更好:
var nums = [1, 2, 3]
nums.forEach(bar)
现在所有流行的代码压缩器都是通过 AST 压缩,因此它们在处理没有分号的 JavaScript 代码时没有问题(因为 JavaScript 不是必须使用分号)。
[依赖自动插入分号机制]的代码是非常安全的,是完全合法的 JavaScript 代码,各浏览器都能正确解析;Closure compiler、yuicompressor、packer 及 jsmin 都能正确压缩。没有任何性能影响。
抱歉,我不是向你说教,这个语言的社区领导者在撒谎,并且害怕告诉你真相。真是羞耻。我建议,先了解 JavaScript 语句是如何结束的以及什么情况不会结束,之后你可以写出漂亮的代码。
一般来说,\n
结束语句,除非:
.
或 ,
结束。--
或 ++
,这时它将递减或递增下一个 token。for()
, while()
, do
, if()
, 或 else
,并且没有 <span class="p">{</span>
。[
, (
, +
, *
, /
, -
, ,
, .
,或者是二进制操作符——它们只能出现在一个表达式的两个操作数之间。第一条显而易见。像这些情况:JSON 或括号内有 \n
字符;一个 var
多行声明,每行以 ,
结束,即使是 JSLint 都没问题。
第二条很怪。我从没有看到这种写法 i\n++\nj
。事实上,它被解析为 i; ++j
,而不是 i++; j
。
第三条很好理解。if (x)\ny()
等于 if (x) { y() }
。这个语句直到遇到一个语句块或语句才结束。
;
是一个合法的 JavaScript 语句,所以 if(x);
等于 if(x){}
或 “If x, do nothing.” 。这更多用于循环,这时循环测试同时也是更新函数。不常见,但不是没听过。
第四条通常是那些因循守旧的人提到的情况:“不,你需要分号!”。但是,事实证明,如果你的意思是这些行不是上一行的连续行,那么在这些行之前加上分号非常容易。例如
foo();
[1,2,3].forEach(bar);
可以这么写:
foo()
;[1,2,3].forEach(bar)
这么做的好处是,一旦你习惯了以 (
或 [
开始的行没有分号,你会很容易注意到行首的分号。
结束引用 “An Open Letter to JavaScript Leaders Regarding Semicolons”
由 Ivan Yan 翻译,译文采用知识共享署名-非商业性使用-相同方式共享 4.0 国际许可协议,意见反馈。
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原文链接 : https://fungleo.blog.csdn.net/article/details/77934448
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