boxed VS async

I was happy when Promise became available, but in retrospect I'd wish we would have skipped ahead and gotten Observable (e.g: https://rxjs.dev/) instead to enable more powerful functionality and composition etc.

In Typescript dealing with rejection is also painful since rejection reasons can't be guaranteed to be Error even when you always take care of that. And it can't help you guarantee that you're handling all types of errors thrown. For that purpose I'm thinking of using https://github.com/supermacro/neverthrow#readme or https://swan-io.github.io/boxed.

Agree that try/catch is verbose and not terribly ergonomic, but my solution has been to treat errors as values rather than exceptions, by default. It's much less painful to achieve this if you use a library with an implementation of a Result type, which I admin is a bit of a painful workaround, but worth it. I've recently been using: https://github.com/swan-io/boxed.

By far the greatest benefit is being able to sanely implement a type-safe API. To me, it is utter madness throwing custom extensions of the Error class arbitrarily deep in the call-stack, and then having a catch handler somewhere up the top hoping that each error case is matched and correctly translated to the intended http response (at least this seems to be a common alternative).

Well you could just install the async package which has lots of useful functions like mapLimit which will reduce the burden and only run a number in parallel.

Have you checked out the docs for the async library they are using?

Edit:2. What's a good library that takes care of common async patterns? (Something like async)

Async/await is certainly not promises. In fact it would be much better implemented without promises as I proposed here: https://es.discourse.group/t/callback-based-simplified-async...

I would even say that async/await is anti-promise, it takes the main functionality of promises, a caching layer for results and errors that allows you to add the code continuation later and elsewhere (which is a major footgun imo) and coerces the execution flow back to going on the next line and provided immediately at compile time which results in a cleaner flow but not as clean, stateless, efficient or functional as if you were to remove the promises completely. Having an additional caching layer and state machine around every asynchronous function call is quite inefficient.

The essence of async/await is not promises, it's the underlying javascript generator (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...) functionality combined with asynchronous code to stop and start the generator. It's the ability to pause and resume function execution based on asynchronous operations.

The promise functionality, the caching layer and state machine for results is basically sanitized away with async/await, it becomes dead-weight computation. The only benefit of promises in async/await code is being able to more easily interface with other promise laden code which you don't need once you have async/await and a library like https://www.npmjs.com/package/async for more complex cases.

Note that promises based async/await is also a mess of an implementation that breaks stack traces and needs to support tons of odd statement corner cases (basically anything that can return an object that could be a promise) whereas a continuation passing style async/await would be a much simpler implementation that would only apply to function calls and maintain stack traces. We get that stack trace support automatically because of the great work of whoever implemented javascript generators which seem to already carry stack traces across paused/resumed functions (if you don't wrap in promises).

The nodejs async module: https://github.com/caolan/async provides 2 similar methods, async.waterfall and async.series.

With async I'd simply use async.series().

I don't understand. Sure you could spawn a ton of processes, but things might be bogged down. There are utilities out there for doing work queues.... so only N workers are running at any one time. The async library has some utilities for that. https://github.com/caolan/async

The documentation of asyncjs is quite straightforward and easy to read. As we've only seen a couple of use cases in this article, I'd recommend to go the asyncjs documentation and check out other possibilities with the library. You can also try to replicate the same using async/await to solidify your understanding of where the library might still make sense.

It basically was tons and tons of callbacks. They'd nest weirdly deep and be a pain to work with. If you're curious, here's a link to one of my favorite JavaScript libraries from those days - it gave you a bunch of neat utilities for dealing with async code.

api(function(result){ api2(function(result2){ api3(function(result3){ // do work }); });}); Which I could use a library like async for anyway, with something like: