This is more or less what RxJS calls an Observable (except with nicer syntax). Here's a very nice table that makes the lack of this feature in ESnext seem like a strange omission:

https://danreynolds.ca/images/tech/push-pull.png

Asynchronous iterators / observables are so much more useful that synchronous iterators that they should've added that to the standard first.

Wouldn't it be wonderful if ESnext allowed you to write event loops that maintain state with block scope variables instead of all the hacks we have to resort to now?

EDIT: RxJS is mentioned in the README. What I like about this is that it doesn't try to implement the kitchen sink and is a fairly atomic dependency. Now if we could just get to where we don't need transpilers anymore, that would be nice.

An interesting alternative to the library mentioned here is that IxJS is the RxJS team's own implementation of the sorts of operators that Axax is trying to provide, though for both ordinary iterators and async iterators: https://github.com/ReactiveX/IxJS

IxJS gets the benefits of trying to share as much as possible the same API as RxJS, making it really easy to use bits of IxJS and RxJS in the same project, depending on use case.