ES6 Promise.all progress

Question

I have several promises that I need to resolve before going further.

Promise.all(promises).then((results) => {   // going further });  

Is there any way I can have the progress of the Promise.all promise?

From the doc, it appears that it is not possible. And this question doesn't answer it either.

So:

• Don't you agree that this would be useful? Shouldn't we query for this feature?
• How can one implement it manually for now?

Answer 1

I've knocked up a little helper function that you can re-use.

Basically pass your promises as normal, and provide a callback to do what you want with the progress..

function allProgress(proms, progress_cb) {    let d = 0;    progress_cb(0);    for (const p of proms) {      p.then(()=> {            d ++;        progress_cb( (d * 100) / proms.length );      });    }    return Promise.all(proms);  }    function test(ms) {    return new Promise((resolve) => {      setTimeout(() => {         console.log(`Waited ${ms}`);         resolve();       }, ms);    });  }      allProgress([test(1000), test(3000), test(2000), test(3500)],    (p) => {       console.log(`% Done = ${p.toFixed(2)}`);  });

Answer 2

You can add a .then() to each promise to count whos finished. something like :

var count = 0;    var p1 = new Promise((resolve, reject) => {    setTimeout(resolve, 5000, 'boo');  });   var p2 = new Promise((resolve, reject) => {    setTimeout(resolve, 7000, 'yoo');  });   var p3 = new Promise((resolve, reject) => {    setTimeout(resolve, 3000, 'foo');  });     var promiseArray = [    p1.then(function(val) {      progress(++count);       return val     }),     p2.then(function(val) {      progress(++count);       return val     }),     p3.then(function(val) {      progress(++count);       return val     })  ]    function progress(count) {    console.log(count / promiseArray.length);  }    Promise.all(promiseArray).then(values => {     console.log(values);  });