Is there a version of setTimeout that returns an ES6 promise?

Question

Similar to this question, but rather than asking about how promises work in general, I specifically want to know:

What is the standard/best way to wrap setTimeout in something that returns a Promise? I'm thinking something like Angular's $timeout function, but not Angular specific.

Answer 1

In Browsers

First of all no - there is no built in for this. Lots of libraries that enhance ES2015 promises like bluebird whip with it.

I think the other answer conflates executing the function and a delay, it also creates timeouts that are impossible to cancel. I'd write it simply as:

function delay(ms){     var ctr, rej, p = new Promise(function (resolve, reject) {         ctr = setTimeout(resolve, ms);         rej = reject;     });     p.cancel = function(){ clearTimeout(ctr); rej(Error("Cancelled"))};     return p;  } 

Then you can do:

delay(1000).then(/* ... do whatever */); 

Or

 doSomething().then(function(){ return delay(1000); }).then(doSomethingElse); 

If we only want the basic functionality in ES2015, it's even simpler as:

let delay = ms => new Promise(r => setTimeout(r, ms)); 

In Node

You can use util.promisify on setTimeout to get a delay function back - meaning you don't have to use the new Promise constructor anymore.

Answer 2

Here's how I'd implement it:

function delay(duration, func) {   var args = Array.prototype.slice.call(arguments, 2);    return new Promise(function (resolve) {     setTimeout(function () {       resolve(func.apply(null, args));     }, duration);   }); } 

(ES5-syntax intentionally chosen)

But maybe there's a common library that already does this, or a better way to do it.