Array.prototype[@@iterator]()

@@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()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]();
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