5 ms·

I'm not usually a JS person, but you can do the same thing with Promises too, right? Did JS Solve(tm) "colored" functions?

shakow 6y ago
> but you can do the same thing with Promises too, right? No, Promises can only be interacted with within the async framework. There is no ways to 1. Call an async function/get a Promise in a sync function and 2. “Extract” the value in the promise and use it as naked value. JS would need e.g. a “stop there, wait for the promise to result, unwrap its content and give it to me” instruction to be like Rust in this case.
- jedimastert 6y ago
  You know what, you're right. I thought there was an "unwrap", that's my b
  - shakow 6y ago
    No problem, knowledge comes from suffering ;)
  - resonantjacket5 6y ago
    You can technically wrap the promise and spin lock on it till it resolves. Aka forcibly wait on an async function in a sync function. There are some npm libraries that provide it. I've used a couple times (for some hacky scripts), though obviously don't use it in the browser.
    - pitaj 6y ago
      AFAIK, you can't do this from JS, you have to have some engine integration, as the busy loop in JS will prevent the event loop from working. For instance, this will essentially halt your runtime: let y; Promise.resolve(123).then(x => { y = x; }); while (!y) {} console.log(y)
      - deleted 6y ago
        [deleted]
      - lhorie 6y ago
        Yes, deasync[0] for example, hooks into the Node.js event loop from c++ land [0] https://www.npmjs.com/package/deasync https://www.npmjs.com/package/deasync
mmis1000 6y ago
No, js won't allow you to halt the whole thread to wait for your async function (most runtime implements it as single thread). But kotlin on Java does (while you have absolutely no reason to do that except workaround, you just literally get a slower sync version of that function. It is a escape hole for you to do it sync when something absolutely need it be like that (take a example, the main function))

shakow 6y ago

> but you can do the same thing with Promises too, right? No, Promises can only be interacted with within the async framework. There is no ways to 1. Call an async function/get a Promise in a sync function and 2. “Extract” the value in the promise and use it as naked value. JS would need e.g. a “stop there, wait for the promise to result, unwrap its content and give it to me” instruction to be like Rust in this case.

jedimastert 6y ago
You know what, you're right. I thought there was an "unwrap", that's my b
- shakow 6y ago
  No problem, knowledge comes from suffering ;)
- resonantjacket5 6y ago
  You can technically wrap the promise and spin lock on it till it resolves. Aka forcibly wait on an async function in a sync function. There are some npm libraries that provide it. I've used a couple times (for some hacky scripts), though obviously don't use it in the browser.
  - pitaj 6y ago
    AFAIK, you can't do this from JS, you have to have some engine integration, as the busy loop in JS will prevent the event loop from working. For instance, this will essentially halt your runtime: let y; Promise.resolve(123).then(x => { y = x; }); while (!y) {} console.log(y)
    - deleted 6y ago
      [deleted]
    - lhorie 6y ago
      Yes, deasync[0] for example, hooks into the Node.js event loop from c++ land [0] https://www.npmjs.com/package/deasync https://www.npmjs.com/package/deasync

mmis1000 6y ago

No, js won't allow you to halt the whole thread to wait for your async function (most runtime implements it as single thread). But kotlin on Java does (while you have absolutely no reason to do that except workaround, you just literally get a slower sync version of that function. It is a escape hole for you to do it sync when something absolutely need it be like that (take a example, the main function))