javascript - 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)}`);
});