Discussion on "Async by default: JavaScript++"

Steven Olsen · 2022-11-01T17:01:21.901Z

Originally appeared on my Medium blog. Promises are pure genius, and were a significant addition to the JavaScript language in ES2015, built on the shoulders of giants. Now I’m convinced they’re all that developers need to handle any asynchronous si...

I agree with Paul-Sebastian Manole here. Also let's not forget how the JavaScript work behind the scenes. Promises are sent to the event loop to be processed once the stack is clear. There is a reason async functions are different from synchronous code that we write.

Hi Manik, thanks for the comment. You're right, JS is single threaded, but Promises technically use a separate "micro-queue" which recieved precendence over the event loop.

In either case, I mentioned "similar to multi-threading concepts" because of that fact of queues vs. threads. So you're correct, they are not the same!

But, if for a moment we set aside starvation (which is a real concern), and also web workers/etc -- then we really can conceptualize Promises as threads! And it's a very powerful way to think about them.

I've written up an Advanced JavaScript Promise slide deck; if you're interested I'll post the link.

Steven Olsen sure would love to read. Drop me a link 👍

Very good article for all of us.

I think it could create extra confusion.

Also, the autoboxing thing you describe doesnt happen. If the thing isn't a promise, await doesn't make it a promise. It just does nothing.

That's why it's called JavaScript++, it's not backwards compatible and requires a new mental model 😉.

You could be right Eric Kwoka, I'm not familiar with the implementation details. That sounds like an efficiency optimization, though. But conceptually, to cover all the cases in a uniform way, the auto-boxing strategy could work.

(Promises are so cool. Just try Promise.resolve(Promise.resolve(5)) if you don't believe me, lol.)

But actually, I introduced it more as a (valid) concept to bridge us over to the async-by-default model.

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Async by default: JavaScript++

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