How can I measure the execution time of a npm/yarn task/script?

Question

How can I measure the execution time of a npm/yarn task on the command line without modifying the scripts.

In my special use case I want to execute an existing E2E-Test (yarn test:e2e) 100 times and take the average value.

Answer 1

Use the following command in unix

time npm run build

For windows use this command

Measure-Command { start-process npm 'run build' -wait}

Answer 2

You could use the npm package gnomon:

A command line utility, a bit like moreutils's ts, to prepend timestamp information to the standard output of another command.

Install it like this:

$ npm i -g gnomon

With this you could run:

$ yarn install | gnomon

And it might give you an output like this:

$ yarn install | gnomon 
   0.5327s   yarn install v1.9.4
   1.9652s   [1/4] Resolving packages...
   0.0160s   success Already up-to-date.
   0.0163s   Done in 2.38s.
   0.0003s   

     Total   2.5315s

Answer 3

If you don't want any global or even local dependencies for this, or you don't want something that only works on unixy operating systems, this is almost trivially achieved with a simple .js file and an equally simple npm script refinement:

{
  ...
  "scripts: {
    "time": "node mark.js",
    "start": "npm run time && ...whatever 'start' was before... && npm run time",
  },
  ...
}

With that mark.js file being the almost trivial following code:

const fs = require("fs"); // or import fs from "fs"; if you're working on modern JS

const timingFile = `.timing`;

if(fs.existsSync(timingFile)) {
  const end = Date.now();
  const start = fs.readFileSync(timingFile);
  fs.unlinkSync(timingFile);
  console.log(`Runtime: ${(end - start)/1000}s`);
} else { fs.writeFileSync(timingFile, `${Date.now()}`, `utf8`); }