Combination of async function + await + setTimeout

Question

I am trying to use the new async features and I hope solving my problem will help others in the future. This is my code which is working:

  async function as         


        

Answer 1

If you would like to use the same kind of syntax as setTimeout you can write a helper function like this:

const setAsyncTimeout = (cb, timeout = 0) => new Promise(resolve => {
    setTimeout(() => {
        cb();
        resolve();
    }, timeout);
});

You can then call it like so:

const doStuffAsync = async () => {
    await setAsyncTimeout(() => {
        // Do stuff
    }, 1000);

    await setAsyncTimeout(() => {
        // Do more stuff
    }, 500);

    await setAsyncTimeout(() => {
        // Do even more stuff
    }, 2000);
};

doStuffAsync();

I made a gist: https://gist.github.com/DaveBitter/f44889a2a52ad16b6a5129c39444bb57

Answer 2

The following code works in Chrome and Firefox and maybe other browsers.

function timeout(ms) {
    return new Promise(resolve => setTimeout(resolve, ms));
}
async function sleep(fn, ...args) {
    await timeout(3000);
    return fn(...args);
}

But in Internet Explorer I get a Syntax Error for the "(resolve **=>** setTimeout..."

Answer 3

Your sleep function does not work because setTimeout does not (yet?) return a promise that could be awaited. You will need to promisify it manually:

function timeout(ms) {
    return new Promise(resolve => setTimeout(resolve, ms));
}
async function sleep(fn, ...args) {
    await timeout(3000);
    return fn(...args);
}

Btw, to slow down your loop you probably don't want to use a sleep function that takes a callback and defers it like this. I'd rather recommend to do something like

while (goOn) {
  // other code
  var [parents] = await Promise.all([
      listFiles(nextPageToken).then(requestParents),
      timeout(5000)
  ]);
  // other code
}

which lets the computation of parents take at least 5 seconds.

Answer 4

The quick one-liner, inline way

 await new Promise(resolve => setTimeout(resolve, 1000));

Answer 5

Since Node 7.6, you can combine the functions promisify function from the utils module with setTimeout() .

Node.js

const sleep = require('util').promisify(setTimeout)

Javascript

const sleep = m => new Promise(r => setTimeout(r, m))

Usage

(async () => {
    console.time("Slept for")
    await sleep(3000)
    console.timeEnd("Slept for")
})()

Answer 6

await setTimeout(()=>{}, 200);

Will work if your Node version is 15 and above.