I think writing an effect library yourself is a tough ask, but some of them have gotten really, really good. And they get you things that are simply not possible with promise. Check out Effection if you want a more vanilla javascript syntax, or Effect if you're really into expressing things functionally.
Is it safe to just "stop calling next() on a generator?" like the post suggest?
To me that sounds like dropping the task on the floor. Specifically, this will not invoke any finally {} blocks:
More correctly, you should invoke `return()` on the generator. Otherwise, you won't provide execution guarantees. This is how Effection does it. There is no equivalent in async functions, so it sounds like the same problem would apply to the GC technique.
JavaScript generators are unmined gold! We've done a lot of usage of JavaScript generators as delimited continuations; using them to implement the classic shift/reset operations in JavaScript. https://github.com/thefrontside/continuation