AsyncIterator.prototype[Symbol.asyncIterator]()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since January 2020.

AsyncIterator 实例的 [Symbol.asyncIterator]() 方法实现了异步可迭代协议并允许内置的异步迭代器被大多数期望异步迭代器的语法所接受,如 for await...of 循环。它返回 this 的值,即异步迭代器对象本身。

尝试一下

const map1 = new Map();

map1.set("0", "foo");
map1.set(1, "bar");

const iterator1 = map1[Symbol.iterator]();

for (const item of iterator1) {
  console.log(item);
}
// Expected output: Array ["0", "foo"]
// Expected output: Array [1, "bar"]

语法

js
asyncIterator[Symbol.asyncIterator]()

参数

无。

返回值

this 的值,即异步迭代器对象本身。

示例

使用 for await...of 循环进行迭代

请注意,你很少需要直接调用该方法。[Symbol.asyncIterator]() 方法的存在使得所有内置的异步迭代器都成为异步可迭代对象,而像 for await...of 循环这样的迭代语法会自动调用该方法来获取异步迭代器来进行循环。

js
const asyncIterator = (async function* () {
  yield 1;
  yield 2;
  yield 3;
})();
(async () => {
  for await (const value of asyncIterator) {
    console.log(value);
  }
})();
// 输出:1,2,3

规范

Specification
ECMAScript® 2025 Language Specification
# sec-asynciteratorprototype-asynciterator

浏览器兼容性

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desktopmobileserver
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
Deno
Node.js
[Symbol.asyncIterator]

Legend

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Full support
Full support

参见