AsyncIterator
AsyncIterator 对象是通过提供 next() 方法来符合 异步迭代器协议 的对象，该方法将承诺履行返回到迭代器结果对象。AsyncIterator.prototype 对象是一个隐藏的全局对象，所有内置异步迭代器都继承自该对象。它提供了一个返回异步迭代器对象本身的 [Symbol.asyncIterator]() 方法，使异步迭代器也成为 异步可迭代。
¥An AsyncIterator object is an object that conforms to the async iterator protocol by providing a next() method that returns a promise fulfilling to an iterator result object. The AsyncIterator.prototype object is a hidden global object that all built-in async iterators inherit from. It provides an [Symbol.asyncIterator]() method that returns the async iterator object itself, making the async iterator also async iterable.
请注意，AsyncIterator 不是全局对象，尽管将来它会与 异步迭代器助手提案 一起出现。所有内置异步迭代器共享的 AsyncIterator.prototype 对象可以通过以下代码获得：
¥Note that AsyncIterator is not a global object, although it will be in the future with the async iterator helpers proposal. The AsyncIterator.prototype object shared by all built-in async iterators can be obtained with the following code:
const AsyncIteratorPrototype = Object.getPrototypeOf(
Object.getPrototypeOf(Object.getPrototypeOf((async function* () {})())),
);
描述
¥Description
目前，唯一内置的 JavaScript 异步迭代器是 异步生成器函数 返回的 AsyncGenerator 对象。Web API 中还有一些其他内置异步迭代器，例如 ReadableStream。
¥Currently, the only built-in JavaScript async iterator is the AsyncGenerator object returned by async generator functions. There are some other built-in async iterators in web API, such as the one of a ReadableStream.
每个异步迭代器都有一个不同的原型对象，它定义特定异步迭代器使用的 next() 方法。所有这些原型对象都继承自 AsyncIterator.prototype，AsyncIterator.prototype 提供了返回异步迭代器对象本身的 [Symbol.asyncIterator]() 方法，使得异步迭代器也是 异步可迭代。
¥Each of these async iterators have a distinct prototype object, which defines the next() method used by the particular async iterator. All of these prototype objects inherit from AsyncIterator.prototype, which provides an [Symbol.asyncIterator]() method that returns the async iterator object itself, making the async iterator also async iterable.
注意：
AsyncIterator.prototype没有实现[Symbol.iterator]()，因此默认情况下异步迭代器不是 同步可迭代。¥Note:
AsyncIterator.prototypedoes not implement[Symbol.iterator](), so async iterators are not sync iterable by default.
实例方法
示例
使用异步迭代器作为异步迭代器
¥Using an async iterator as an async iterable
所有内置异步迭代器也是异步可迭代的，因此你可以在 for await...of 循环中使用它们：
¥All built-in async iterators are also async iterable, so you can use them in a for await...of loop:
const asyncIterator = (async function* () {
yield 1;
yield 2;
yield 3;
})();
(async () => {
for await (const value of asyncIterator) {
console.log(value);
}
})();
// Logs: 1, 2, 3
规范
| Specification |
|---|
| ECMAScript Language Specification # sec-asynciteratorprototype |
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也可以看看
¥See also