Map.prototype[@@iterator]()

@@iterator 属性的初始值与 entries 属性的初始值是同一个函数对象。

语法

myMap[Symbol.iterator]

返回值

map 的 iterator 函数默认就是 entries() 函数。

示例

使用 [@@iterator]()

var myMap = new Map();
myMap.set('0', 'foo');
myMap.set(1, 'bar');
myMap.set({}, 'baz');

var mapIter = myMap[Symbol.iterator]();
//返回的其实是个generator
console.log(mapIter.next().value); // ["0", "foo"]
console.log(mapIter.next().value); // [1, "bar"]
console.log(mapIter.next().value); // [Object, "baz"]

for..of中使用[@@iterator]() 

var myMap = new Map();
myMap.set('0', 'foo');
myMap.set(1, 'bar');
myMap.set({}, 'baz');

for (const entry of myMap) {
  console.log(entry);
}
// ["0", "foo"]
// [1, "bar"]
// [{}, "baz"]

for (var v of myMap) {
  console.log(v);
}

// 0: foo
// 1: bar
// [Object]: baz

规范

Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
Map.prototype[@@iterator]()
Standard Initial definition.
ECMAScript Latest Draft (ECMA-262)
Map.prototype[@@iterator]()
Draft  

浏览器兼容

Update compatibility data on GitHub
Desktop Mobile Server
Chrome Edge Firefox Internet Explorer Opera Safari Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet Node.js
@@iterator Chrome Full support 43 Edge Full support 12 Firefox Full support 36
Full support 36
No support 27 — 36
Notes Alternate Name
Notes A placeholder property named @@iterator is used.
Alternate Name Uses the non-standard name: @@iterator
No support 17 — 27
Notes Alternate Name
Notes A placeholder property named iterator is used.
Alternate Name Uses the non-standard name: iterator
IE No support No Opera Full support 30 Safari Full support Yes WebView Android Full support 43 Chrome Android Full support 43 Firefox Android Full support 36
Full support 36
No support 27 — 36
Notes Alternate Name
Notes A placeholder property named @@iterator is used.
Alternate Name Uses the non-standard name: @@iterator
No support 17 — 27
Notes Alternate Name
Notes A placeholder property named iterator is used.
Alternate Name Uses the non-standard name: iterator
Opera Android Full support 30 Safari iOS Full support Yes Samsung Internet Android Full support 4.0 nodejs Full support 0.12

Legend

Full support  
Full support
No support  
No support
See implementation notes.
See implementation notes.
Uses a non-standard name.
Uses a non-standard name.

另见