在此页

• 描述
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

The well-known Symbol.iterator symbol specifies the default iterator for an object. Used by for...of .

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

描述

Whenever an object needs to be iterated (such as at the beginning of a for..of loop), its @@iterator method is called with no arguments, and the returned iterator is used to obtain the values to be iterated.

Some built-in types have a default iteration behavior, while other types (such as Object ) do not. The built-in types with a @@iterator method are:

• Array.prototype[@@iterator]()
• TypedArray.prototype[@@iterator]()
• String.prototype[@@iterator]()
• Map.prototype[@@iterator]()
• Set.prototype[@@iterator]()

另请参阅 Iteration protocols 了解更多信息。

特性属性在 Symbol.iterator
可写	no
可枚举	no
可配置	no

范例

User-defined iterables

We can make our own iterables like this:

var myIterable = {}
myIterable[Symbol.iterator] = function* () {
    yield 1;
    yield 2;
    yield 3;
};
[...myIterable] // [1, 2, 3]
					

Or iterables can be defined directly inside a class or object using a computed property :

class Foo {
  *[Symbol.iterator] () {
    yield 1;
    yield 2;
    yield 3;
  }
}
const someObj = {
  *[Symbol.iterator] () {
    yield 'a';
    yield 'b';
  }
}
[...new Foo] // [ 1, 2, 3 ]
[...someObj] // [ 'a', 'b' ]
					

Non-well-formed iterables

If an iterable's @@iterator method does not return an iterator object, then it is a non-well-formed iterable. Using it as such is likely to result in runtime exceptions or buggy behavior:

var nonWellFormedIterable = {}
nonWellFormedIterable[Symbol.iterator] = () => 1
[...nonWellFormedIterable] // TypeError: [] is not a function
					

规范

规范
ECMAScript (ECMA-262) The definition of 'Symbol.iterator' in that specification.

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	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 43	Edge 12	Firefox 36	IE No	Opera 30	Safari 10	WebView Android 43	Chrome Android 43	Firefox Android 36	Opera Android 30	Safari iOS 10	Samsung Internet Android 4.0	nodejs 0.12

图例

完整支持

完整支持

不支持

不支持

另请参阅

• Iteration protocols
• Array.prototype[@@iterator]()
• TypedArray.prototype[@@iterator]()
• String.prototype[@@iterator]()
• Map.prototype[@@iterator]()
• Set.prototype[@@iterator]()

元数据

• 最后修改： May 3, 2020

相关话题

1. 标准内置对象
2. Symbol
3. 特性
   1. Symbol.asyncIterator
   2. Symbol.hasInstance
   3. Symbol.isConcatSpreadable
   4. Symbol.iterator
   5. Symbol.match
   6. Symbol.matchAll
   7. Symbol.prototype.description
   8. Symbol.replace
   9. Symbol.search
   10. Symbol.species
   11. Symbol.split
   12. Symbol.toPrimitive
   13. Symbol.toStringTag
   14. Symbol.unscopables
4. 方法
   1. Symbol.for()
   2. Symbol.keyFor()
   3. Symbol.prototype.toSource()
   4. Symbol.prototype.toString()
   5. Symbol.prototype.valueOf()
   6. Symbol.prototype[@@toPrimitive]
5. 继承：
6. Function
7. 特性
   1. Function.arguments
   2. Function.caller
   3. Function.displayName
   4. Function.length
   5. Function.name
8. 方法
   1. Function.prototype.apply()
   2. Function.prototype.bind()
   3. Function.prototype.call()
   4. Function.prototype.toSource()
   5. Function.prototype.toString()
9. Object
10. 特性
    1. Object.prototype.__proto__
    2. Object.prototype.constructor
11. 方法
    1. Object.prototype.__defineGetter__()
    2. Object.prototype.__defineSetter__()
    3. Object.prototype.__lookupGetter__()
    4. Object.prototype.__lookupSetter__()
    5. Object.prototype.hasOwnProperty()
    6. Object.prototype.isPrototypeOf()
    7. Object.prototype.propertyIsEnumerable()
    8. Object.prototype.toLocaleString()
    9. Object.prototype.toSource()
    10. Object.prototype.toString()
    11. Object.prototype.valueOf()
    12. Object.setPrototypeOf()