Determine how long javascript promise took

Question

does anyone know of a way I can determine how long each promise took to execute in Promise.all([...])?

Thanks in advance!

Possible duplicate of [Benchmark Asynchronous Code (Benchmark.js, Node.js)](https://stackoverflow.com/questions/31624055/benchmark-asynchronous-code-benchmark-js-node-js) — I wrestled a bear once., Feb 08 '18 at 13:48
I don't think this is a good duplicate. To OP: you can measure each promise separately before passing them to Promise.all. — dfsq, Feb 08 '18 at 13:50
measuring each one individually is the only way to do it if you want individual measurements. the duplicate link explains how to do that. — I wrestled a bear once., Feb 08 '18 at 13:51
@Trung Tran here is a simple way of doing this: http://plnkr.co/edit/mS2n71Vte6VPbl7jl6nl?p=preview You can wrap whatever you want. — dfsq, Feb 08 '18 at 14:03

score 2 · Answer 1 · answered Feb 08 '18 at 14:07

You could make your own Promise.all function.

Below is an example, that returns timings for each promise in an array it returns, the array also contains the results of the promises too, but of course in this demo my wait function has nothing to return.

function wait(ms) {
  return new Promise((resolve) => {
    setTimeout(resolve, ms);
  });
}

async function myPromiseAll(promises) {
  const starttime = new Date().getTime();
  const timings = [];
  promises.forEach((prom, ix) => {
    prom.then(() => {
      timings[ix] = new Date().getTime() - starttime;
    });
  });
  const result = await Promise.all(promises);
  return {result, timings};
}

async function run() {
  console.log("Starting stuff.");
  const ret = await myPromiseAll([
    wait(1000), wait(2000)]);
  console.log(ret.timings);
  // console.log(ret.result); result of promises
}

run();

Determine how long javascript promise took

1 Answers1