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• 句法
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

@@iterator method is part of The iterable protocol , that defines how to synchronously iterate over a sequence of values.

The initial value of the @@iterator property is the same function object as the initial value of the values() 特性。

句法

arr[Symbol.iterator]()
					

返回值

The initial value given by the values() iterator . By default, using arr[Symbol.iterator] will return the values() 函数。

范例

Iteration using for...of loop

HTML

<ul id="letterResult">
</ul>
					

JavaScript

var arr = ['a', 'b', 'c'];
var eArr = arr[Symbol.iterator]();
var letterResult = document.getElementById('letterResult');
// your browser must support for..of loop
// and let-scoped variables in for loops
// const and var could also be used
for (let letter of eArr) {
 letterResult.innerHTML += "<li>" + letter + "</li>";
}
					

结果

Alternative iteration

var arr = ['a', 'b', 'c', 'd', 'e'];
var eArr = arr[Symbol.iterator]();
console.log(eArr.next().value); // a
console.log(eArr.next().value); // b
console.log(eArr.next().value); // c
console.log(eArr.next().value); // d
console.log(eArr.next().value); // e
					

Use Case for brace notation

The use case for this syntax over using the dot notation ( Array.prototype.values() ) is in a case where you don't know what object is going to be ahead of time. If you have a function that takes an iterator and then iterate over the value, but don't know if that Object is going to have a [Iterable].prototype.values method. This could be a built-in object like String object or a custom object.

function logIterable(it) {
 if (!(Symbol.iterator in Object.getPrototypeOf(it)
 /* or "Symbol.iterator in Object.__proto__"
    or "it[Symbol.iterator]" */)) {
   console.log(it, ' is not an iterable object...');
   return;
 }
 var iterator = it[Symbol.iterator]();
  // your browser must support for..of loop
  // and let-scoped variables in for loops
  // const and var could also be used
  for (let letter of iterator) {
      console.log(letter);
  }
}
// Array
logIterable(['a', 'b', 'c']);
// a
// b
// c
// string
logIterable('abc');
// a
// b
// c
logIterable(123);
// 123 " is not an iterable object..."
					

规范

规范
ECMAScript (ECMA-262) The definition of 'Array.prototype[@@iterator]()' in that specification.

浏览器兼容性

The compatibility table in 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 38	Edge 12	Firefox 36 36 不支持 27 — 36 Alternate Name A placeholder property named @@iterator 被使用。 Alternate Name Uses the non-standard name: @@iterator 不支持 17 — 27 Alternate Name A placeholder property named iterator 被使用。 Alternate Name Uses the non-standard name: iterator	IE No	Opera 25	Safari 10	WebView Android 38	Chrome Android 38	Firefox Android 36 36 不支持 27 — 36 Alternate Name A placeholder property named @@iterator 被使用。 Alternate Name Uses the non-standard name: @@iterator 不支持 17 — 27 Alternate Name A placeholder property named iterator 被使用。 Alternate Name Uses the non-standard name: iterator	Opera Android 25	Safari iOS 10	Samsung Internet Android 3.0	nodejs 0.12

图例

完整支持

完整支持

不支持

不支持

见实现注意事项。

使用非标名称。

另请参阅

• Array.prototype.keys()
• Array.prototype.entries()
• Array.prototype.forEach()
• Array.prototype.every()
• Array.prototype.some()
• Array.prototype.values()

元数据

• 最后修改： Jul 28, 2020

相关话题

1. 标准内置对象
2. Array
3. 特性
   1. Array.prototype.length
   2. Array.prototype[@@unscopables]
4. 方法
   1. Array.from()
   2. Array.isArray()
   3. Array.of()
   4. Array.prototype.concat()
   5. Array.prototype.copyWithin()
   6. Array.prototype.entries()
   7. Array.prototype.every()
   8. Array.prototype.fill()
   9. Array.prototype.filter()
   10. Array.prototype.find()
   11. Array.prototype.findIndex()
   12. Array.prototype.flat()
   13. Array.prototype.flatMap()
   14. Array.prototype.forEach()
   15. Array.prototype.includes()
   16. Array.prototype.indexOf()
   17. Array.prototype.join()
   18. Array.prototype.keys()
   19. Array.prototype.lastIndexOf()
   20. Array.prototype.map()
   21. Array.prototype.pop()
   22. Array.prototype.push()
   23. Array.prototype.reduce()
   24. Array.prototype.reduceRight()
   25. Array.prototype.reverse()
   26. Array.prototype.shift()
   27. Array.prototype.slice()
   28. Array.prototype.some()
   29. Array.prototype.sort()
   30. Array.prototype.splice()
   31. Array.prototype.toLocaleString()
   32. Array.prototype.toSource()
   33. Array.prototype.toString()
   34. Array.prototype.unshift()
   35. Array.prototype.values()
   36. Array.prototype[@@iterator]()
   37. get Array[@@species]
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()