joepie91/delay-promise.js

As I find myself ending up on this very page approx. once a week (copy pasting @PabloCorso version), here's a Node.js specific alternative for my future self 😄

const delay = require("util").promisify(setTimeout)

Hi @berstend - I don't think util.promisify does what you hoped.

It expects a function whose callback argument is last. setTimeout's callback method is first, and timeout in milliseconds is 2nd. (The rarely used context arg is 3rd.)

This necessitates a wrapper function, I use something similar to https://gist.github.com/joepie91/2664c85a744e6bd0629c#gistcomment-2555399 :

const delay = ms => new Promise(yea => setTimeout(yea, ms));

delay(1000)
  .then(() => console.log('waited 1000 secs'))

@justml I'm fairly certain you are wrong as it's in nodejs's documentation

@justml @jgerstle

I confirm that the following code works perfectly with Node.js:

const wait = require('util').promisify(setTimeout);

(async () => {
    console.log('Wait...');
    await wait(1000);
    console.log('...a second.');
})();

Hello future self, here's the TypeScript version for your copy/pasting pleasure:

const delay = (ms: number) => new Promise(_ => setTimeout(_, ms))

and my favorite JS version:

const delay = ms => new Promise(_ => setTimeout(_, ms))

You forget to clear the setTimeout

const delay = async <T>(timeout: number, value?: T) => {
    return new Promise((resolve) => {
        const timeoutId = setTimeout(() => {
            resolve(value);
            clearTimeout(timeoutId);
        }, timeout);
    });
};

@tolotrasmile That shouldn't be necessary, since this is a setTimeout, not a setInterval. A setTimeout only ever fires once, so once you're in the callback, there is nothing to clearTimeout anymore.

clearTimeout is basically just for cancelling a setTimeout that has not yet occurred.

For nodeJS only

import { setTimeout } from "timers/promises";

await setTimeout(3000, value);