Learn how to write a promise based delay function and then use it in async await to see how much it simplifies code over setTimeout.

Lets say you want to call a function after 1s, 2s, 3s. You can use setTimeout, or you can wrap it up into a simple delay function that works with async/await

 

We want to conver this code

const run = (cb) => {  setTimeout(() => {    cb('1s');    setTimeout(() => {      cb('2s');      setTimeout(() => {        cb('3s');      }, 1000);    }, 1000);  }, 1000);}

 

to:

const delay = (ms) => new Promise(res => setTimeout(res, ms));const runAsync = async (cb) => {  await delay(1000);  cb('1s');  await delay(1000);  cb('2s');  await delay(1000);  cb('3s');}runAsync((time) => console.log(time));