JavaScript sleep Function

Discussion

1. Thomas BROYER

   This is not a “sleep” function, as it doesn’t block the current (main) thread, it’s more an “after” function; à la Golang Sleep vs. After: https://golang.org/pkg/time/
• Thomas BROYER

  (of course, reading from the channel in Golang would block, so not really an appropriate comparison either, but you get the idea: things can happen between the call to the function and the “callback” happens)
• MaxArt

  Of course, nothing like the classic ‘sleep’ function exists in Javascript – and should never exist, actually. The only blocking thing in Javascript has been a sync AJAX request – a relic of the past.
  It’s just a way to introduce a similar concept, but still in Javascript’s way of coding.
2. selvagsz

   With await, this would look even more sweet,

   await sleep(500);
   // do stuff
   
• MaxArt

  Yes, I was thinking of the same thing. The only thing that bugs me is that every function that uses await should be declared async.
  (Actually, it’s the main complaint about async/await…)
3. Revlift

   This signal callback function I always used my program, sleep await used in synchronus programe
4. Tolis

   Make sure you clear the timeout when the Promise resolves.
5. Claudio

   Not a big fan of this approach.

   Without async/await, wrapping a setTimeout call into a non-blocking Promise does not add any value but readability, not to mention that it prevents the timer from being canceled.
6. Rüdiger

   I agree that this isn’t a solution for a possible sleep function.
   From my point of view it should stop the current process (but not the event handling) and continue (within the same scope when it was called) afterwards.

   Thus, you may call it in a function without the need to split the function into two, which is necessary using the approach above.

   And when already talking about a sleep function, a processMessages() function, similar as in Delphi/Lazarus (Application.processMessages()) is needed too… :)
7. Kay

   Not everyone likes or knows (like me) the magic of arrow functions. Here is the “same” code without =>

   function sleepAsync(time) {
     //return new Promise((resolve) => setTimeout(resolve, time));
       var p = new Promise();
       setTimeout(function() { p.resolve(); }, time);
       return p.promise();  
   }
   
8. Kay

   Ah, and this is usage without arrow function for both:

   // Usage!
   sleep(500).then(function(){
       // Do something after the sleep!
   })
   
9. Vitaliy

   If you also need to clear promised timeout (like setTimeout does), consider this package: https://github.com/vitalets/await-timeout

   import Timeout from 'await-timeout';
   
   async function foo() {
     const timeout = new Timeout();
     try {
       const mainPromise = fetch('https://example.com');
       const timerPromise = timeout.set(1000, 'Rejected by timeout');
       await Promise.race([mainPromise, timerPromise]);
     } catch (e) {
       console.error(e);
     } finally {
       timeout.clear();
     }
   }