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.

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 am @@asyncIterator method that returns the async iterator object itself, making the async iterator also async iterable.

AsyncIterator.prototype[@@asyncIterator]()

Returns the async iterator object itself. This allows async iterator objects to also be async iterable.

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

• async function*
• Iteration protocols