how to add delay before returning a value in javascript function

Question

I need to add a 2 seconds delay before returning a value in Javascript function

function slowFunction(num) {
  console.log("Calling slow function");
 
  // 2 seconds delay here

  return num * 2;
}

What is your use case that requires this delay? And what have you tried? — charlietfl, Jun 05 '21 at 21:33

score 2 · Accepted Answer · answered Jun 05 '21 at 21:36

2

A couple of ways to do this.

I prefer using promises.

function sleep(delay: number): Promise<void>{
   return new Promise( (res) => {
        setTimeout(()=>res(),delay)
   })
}

async function slowFunction(num) {
  console.log("Calling slow function");
  await sleep(2000)
  // 2 seconds delay here

  return num * 2;
}

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function

answered Jun 05 '21 at 21:36

albseb

169
5

Why the slowFunction also returning a promise – Shashank Mishra Jun 06 '21 at 05:47
1

thats because I add async on function. You should check up on how promises work, and how async await works. – albseb Jun 06 '21 at 14:37

how to add delay before returning a value in javascript function

1 Answers1