Array.prototype[@@iterator]() - JavaScript 编辑

@@iterator 属性和 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 values() 返回值相同， arr[Symbol.iterator] 则会返回 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
ECMAScript 2015 (6th Edition, ECMA-262) Array.prototype[@@iterator]()	Standard	首次定义
ECMAScript (ECMA-262) Array.prototype[@@iterator]()	Living Standard

浏览器兼容性

BCD tables only load in the browser

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.

参见

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