Async iterators and the for await..of loop

Overview

Asynchronous iterator objects, such as those returned by promises or generator functions, are iterable with the for await .. of loop.

Feature	Desktop				Mobile
Feature	Chrome	Edge	Firefox	Safari	Chrome Android	Safari iOS
`AsyncIterator`	63	79	57	11.1	63	11.3
`AsyncIterator.@@asyncIterator` The [Symbol.asyncIterator]() method of AsyncIterator instances implements the async iterable protocol and allows built-in async iterators to be consumed by most syntaxes expecting async iterables, such as for await...of loops. It returns the value of this, which is the async iterator object itself.	63	79	57	11.1	63	11.3
`Symbol.asyncIterator` The Symbol.asyncIterator static data property represents the well-known symbol Symbol.asyncIterator. The async iterable protocol looks up this symbol for the method that returns the async iterator for an object. In order for an object to be async iterable, it must have a [Symbol.asyncIterator] key.	63	79	57	11.1	63	11.3
Other
`javascript.statements.for_await_of` The for await...of statement creates a loop iterating over async iterable objects as well as sync iterables. This statement can only be used in contexts where await can be used, which includes inside an async function body and in a module.	63	79	57	12	63	12
Statement
`async iterators` async iterators	63	12	57	7	63	7

1+Supported (version) Not supported ※Has note Sub-feature descriptions sourced from MDN Web Docs (CC BY-SA 2.5)

JAVASCRIPT

// for await...of loop
for await (const chunk of readableStream) {
  process(chunk);
}

Iterate. with Symbol.asyncIterator implementationobject for await...of.

sequential. with Promise Array for await...of.

Symbol.iterator and Symbol.asyncIterator. Compare usage.

Using Async iterators and the for await..of loop
Asynchronous iterator objects, such as those returned by promises or generator functions, are iterable with the for await .. of loop.