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Comment by LargeWu | Hacker News Reader

Let's not pretend javascript Promises and async/await are not magic in the same way some of Rails is. Lots of gotchas and unintuitive behavior, let alone cryptic error messages and stack traces. At least Ruby generally gives pretty useful stack traces. When something breaks, it gives you a pretty clear indication of exactly what line it happened on and what the problem is.

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I love Rails (though criticism of its magic is fair), but this isn’t a good analogy. Async/await is literally syntactic sugar over the Promises abstraction. There’s nothing magic about Promises, and certainly nothing magic about async/await. In fact, I’d argue you’re in for a slower learning curve if you believe there to be magic in these areas.

> In fact, I’d argue you’re in for a slower learning curve if you believe there to be magic in these areas.

I 110% agree with you.

This is Rails striking again!

"Don't look at the magic, just memorize it." might as well be Rails' slogan.

Convention over configuration really just means "Memorize all my conventions, and don't ask why I picked them".

Great for the case where your use-case is in line with the chosen conventions and you don't want to think all that hard (or you just need to pump out content - like a contract agency). Pretty terrible for just about everything else.

Promises and async/await are absolutely not magic. Every JS engineer who is competent quickly learns how the event loop works and how promises work.

Promises/async/await seem very different than Ruby's (and Rails') metaprogramming to me. I'd need an example of a cryptic stack trace to know exactly what you're referring to--half the problem is because of the overuse of anonymous functions that bork the trace. There's an easy solution to that (and it makes the resulting code easier to test as well).

the fact that there is a long chapter in a book series written on the edge cases of javascript[0] leads me to believe that it's not generally well understood either.

0. https://github.com/getify/You-Dont-Know-JS/blob/1st-ed/async...

JS uses an event-loop (which is really just a variation of a message/event queue that we've been using for GUI based applications for decades now). If you understand this, asynchronous code in JS is pretty easy to understand.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Even...

You can go from nothing to mostly full-fledged promises in about 200 lines of code: ex - https://www.promisejs.org/implementing/

async/await is pure sugar on top of promises (it's literally just wrapping the rest of the function in a .then() for you, and coercing the return value of your function to always be a promise)

IMO that's an explicitly different issue than a comparison between Promises/async/await and Ruby's metaprogramming, though.

Not to mention that part of the issue with Promises is the various polyfills invented before broad acceptance, which is a separate can of worms, and a different type of complexity than the (relatively) heavy use of metaprogramming in Ruby (relative to JS).

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