--- title: 'Array.prototype[@@iterator]()' slug: Web/JavaScript/Reference/Global_Objects/Array/@@iterator tags: - Array - ECMAScript 2015 - Iterator - JavaScript - Method - Prototype - 原型 - 参考 - 循环 - 方法 - 迭代 translation_of: Web/JavaScript/Reference/Global_Objects/Array/@@iterator ---
{{JSRef}}

@@iterator 属性和 {{jsxref("Array.prototype.values()", "Array.prototype.values()")}} 属性的初始值是同一个函数对象。

语法

arr[Symbol.iterator]()

返回值

数组的 iterator 方法，默认情况下，与 {{jsxref("Array.prototype.values()", "values()")}} 返回值相同， arr[Symbol.iterator] 则会返回 {{jsxref("Array.prototype.values()", "values()")}} 函数。

示例

使用 for...of 循环进行迭代

var arr = ['a', 'b', 'c', 'd', 'e'];
var eArr = arr[Symbol.iterator]();
// 浏览器必须支持 for...of 循环
for (let letter of eArr) {
  console.log(letter);
}

另一种迭代方式

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) {
  var iterator = it[Symbol.iterator]();
  // 浏览器必须支持 for...of 循环
  for (let letter of iterator) {
      console.log(letter);
  }
}

// Array
logIterable(['a', 'b', 'c']);
// a
// b
// c

// string
logIterable('abc');
// a
// b
// c

规范

规范名称 规范状态 备注
{{SpecName('ES6', '#sec-array.prototype-@@iterator', 'Array.prototype[@@iterator]()')}} {{Spec2('ES6')}} 首次定义
{{SpecName('ESDraft', '#sec-array.prototype-@@iterator', 'Array.prototype[@@iterator]()')}} {{Spec2('ESDraft')}}

浏览器兼容性

{{Compat("javascript.builtins.Array.@@iterator")}}

参见