左侧工具栏是按字母表排序的列表。
JavaScript中基本关键字和常用表达式。
this
this
关键字指向函数的执行上下文。function
function
关键字定义了函数表达式。class
class
关键字定义了类表达式。function*
function*
关键字定义了一个 generator 函数表达式。yield
yield*
async function*
async function
定义一个异步函数表达式。await
[]
{}
/ab+c/i
( )
左边的值是赋值的目标。
object.property
和 object["property"]
).new
new
运算符创建了构造函数实例。new.target
指向new
调用的构造器。super
super
关键字调用父类的构造器....obj
前置/后置自增运算符和前置/后置自减运算符.
A++
A--
++A
--A
一元运算符只有一个操作数.
delete
delete
运算符用来删除对象的属性.void
void
运算符表示表达式放弃返回值.typeof
typeof
运算符用来判断给定对象的类型.+
-
~
!
算术运算符以二个数值(字面量或变量)作为操作数,并返回单个数值。
+
-
/
*
%
比较运算符比较二个操作数并返回基于比较结果的Boolean
值。
in
in运算符用来判断对象是否拥有给定属性
.instanceof
instanceof
运算符判断一个对象是否是另一个对象的实例.<
>
<=
>=
箭头函数
的表示符。如果相等,操作符返回的是Boolean(布尔)类型的true,否则是false。
==
!=
===
!==
在二进制的基础上对数字进行移动操作
<<
>>
>>>
二进制运算符将它们的操作数作为32个二进制位(0或1)的集合,并返回标准的JavaScript数值。
&
|
^
逻辑运算符典型的用法是用于boolean(逻辑)值运算, 它们返回boolean值。
&&
||
(condition ? ifTrue : ifFalse)
条件元素运算符把两个结果中其中一个符合运算逻辑的值返回。
赋值元素符会将右边的操作数的值分配给左边的操作数,并将其值修改为右边操作数相等的值。
=
*=
/=
%=
+=
-=
<<=
>>=
>>>=
&=
^=
|=
[a, b] = [1, 2]
{a, b} = {a:1, b:2}
解构赋值允许你分配数组或者对象变量的属性通过使用规定的语法,其看起来和数组和对象字面量很相似。
,
yield
表达式。[for (x of y) x]
(for (x of y) y)
Specification | Status | Comment |
---|---|---|
ECMAScript 1st Edition (ECMA-262) Expressions |
Standard | Initial definition |
ECMAScript 5.1 (ECMA-262) Expressions |
Standard | |
ECMAScript 2015 (6th Edition, ECMA-262) ECMAScript Language: Expressions |
Standard | New: Spread syntax, rest syntax, destructuring assignment, super keyword. |
ECMAScript Latest Draft (ECMA-262) ECMAScript Language: Expressions |
Draft |
Desktop | Mobile | Server | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Array comprehensions | Chrome No support No | Edge No support No | Firefox No support 30 — 58 | IE No support No | Opera No support No | Safari No support No | WebView Android No support No | Chrome Android No support No | Edge Mobile No support No | Firefox Android No support 30 — 58 | Opera Android No support No | Safari iOS No support No | Samsung Internet Android No support No | nodejs No support No |
async function expression | Chrome Full support 55 | Edge Full support 15 | Firefox Full support 52 | IE No support No | Opera Full support 42 | Safari Full support 10.1 | WebView Android Full support 55 | Chrome Android Full support 55 | Edge Mobile Full support 15 | Firefox Android Full support 52 | Opera Android Full support 42 | Safari iOS Full support 10.1 | Samsung Internet Android Full support 6.0 | nodejs
Full support
7.6.0
|
await | Chrome Full support 55 | Edge Full support Yes | Firefox Full support 52 | IE ? | Opera Full support 42 | Safari Full support 10.1 | WebView Android Full support 55 | Chrome Android Full support 55 | Edge Mobile Full support Yes | Firefox Android Full support 52 | Opera Android Full support 42 | Safari iOS Full support 10.1 | Samsung Internet Android Full support 6.0 | nodejs
Full support
7.6.0
|
class | Chrome Full support 42 | Edge Full support Yes | Firefox Full support 45 | IE No support No | Opera Full support Yes | Safari Full support Yes | WebView Android Full support 42 | Chrome Android Full support 42 | Edge Mobile Full support Yes | Firefox Android Full support 45 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support 4.0 | nodejs
Full support
6.0.0
|
Comma operator | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support 3 | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
Conditional operator (c ? t : f ) | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
delete | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
Destructuring assignment | Chrome Full support 49 | Edge Full support 14 | Firefox
Full support
41
| IE No support No | Opera Full support Yes | Safari Full support 8 | WebView Android Full support 49 | Chrome Android Full support 49 | Edge Mobile Full support 14 | Firefox Android
Full support
41
| Opera Android Full support Yes | Safari iOS Full support 8 | Samsung Internet Android Full support 5.0 | nodejs Full support 6.0.0 |
Expression closures | Chrome No support No | Edge No support No | Firefox No support 3 — 60 | IE No support No | Opera No support No | Safari No support No | WebView Android No support No | Chrome Android No support No | Edge Mobile No support No | Firefox Android No support 4 — 60 | Opera Android No support No | Safari iOS No support No | Samsung Internet Android No support No | nodejs No support No |
function | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
function* | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 26 | IE No support No | Opera Full support Yes | Safari Full support 10 | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 26 | Opera Android Full support Yes | Safari iOS Full support 10 | Samsung Internet Android Full support Yes | nodejs Full support Yes |
Generator comprehensions | Chrome No support No | Edge No support No | Firefox No support 30 — 58 | IE No support No | Opera No support No | Safari No support No | WebView Android No support No | Chrome Android No support No | Edge Mobile No support No | Firefox Android No support 30 — 58 | Opera Android No support No | Safari iOS No support No | Samsung Internet Android No support No | nodejs No support No |
Grouping operator () | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
in | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
instanceof | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
Legacy generator function | Chrome No support No | Edge No support No | Firefox No support 2 — 58 | IE No support No | Opera No support No | Safari No support No | WebView Android No support No | Chrome Android No support No | Edge Mobile No support No | Firefox Android No support 4 — 58 | Opera Android No support No | Safari iOS No support No | Samsung Internet Android No support No | nodejs No support No |
new | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
new.target | Chrome Full support 46 | Edge Full support Yes | Firefox Full support 41 | IE No support No | Opera Full support Yes | Safari Full support Yes | WebView Android Full support 46 | Chrome Android Full support 46 | Edge Mobile Full support Yes | Firefox Android Full support 41 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support 5.0 | nodejs Full support 5.0.0 |
Object initializer | Chrome Full support 1 | Edge Full support Yes | Firefox Full support 1 | IE Full support 1 | Opera Full support Yes | Safari Full support 1 | WebView Android Full support 1 | Chrome Android Full support 18 | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support 1 | Samsung Internet Android Full support Yes | nodejs Full support Yes |
Pipeline operator (|> ) | Chrome No support No | Edge No support No | Firefox
Full support
58
| IE No support No | Opera No support No | Safari No support No | WebView Android No support No | Chrome Android No support No | Edge Mobile No support No | Firefox Android
Full support
58
| Opera Android No support No | Safari iOS No support No | Samsung Internet Android No support No | nodejs No support No |
Property accessors | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
super | Chrome Full support 42 | Edge Full support Yes | Firefox Full support 45 | IE No support No | Opera Full support Yes | Safari Full support Yes | WebView Android Full support 42 | Chrome Android Full support 42 | Edge Mobile Full support Yes | Firefox Android Full support 45 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support 4.0 | nodejs Full support Yes |
this | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
typeof | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
void | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
yield | Chrome Full support 39 | Edge Full support Yes | Firefox
Full support
26
| IE No support No | Opera Full support Yes | Safari Full support 10 | WebView Android Full support 39 | Chrome Android Full support 39 | Edge Mobile Full support Yes | Firefox Android
Full support
26
| Opera Android Full support Yes | Safari iOS Full support 10 | Samsung Internet Android Full support 4.0 | nodejs
Full support
4.0.0
|
yield* | Chrome Full support Yes | Edge Full support Yes | Firefox
Full support
27
| IE No support No | Opera Full support Yes | Safari Full support 10 | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android
Full support
27
| Opera Android Full support Yes | Safari iOS Full support 10 | Samsung Internet Android Full support Yes | nodejs
Full support
4.0.0
|