Javascript generators for real life usage

Generator functions can yield for a moment, and then continue execution. 
It goes great with coroutines and promises. Let’s adopt by examples:

First: Synchronous iteration of infinite sequence

Second: Asynchronous iteration of finite sequence

Third: Asynchronous sequential process of items

Fourth: Asynchronous process sequence until breaks

What do you think about last example?

Do you know how to deal with asynchronous iteration of infinite sequence?

Thanks for your comments.