NodeJs - Async/Await inside controller

Question

I have this simple example to my controller and doesn't work as expected

export let create = async (req: Request, res: Response) => {

   console.log("START");
   await setTimeout(() => {
      console.log("MIDDLE");
   }, 1000);
   console.log("END");
   return res.json({ data: null });

};

Output: START,END,MIDDLE

EXPECT: START,MIDDLE,END

`setTimeout` returns a **number**, not a promise. Only if you `await` a promise does the execution actually "wait". — Felix Kling, Dec 27 '17 at 14:31

score 2 · Accepted Answer · answered Dec 27 '17 at 14:32

2

try:

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

answered Dec 27 '17 at 14:32

Lev Kuznetsov

3,520
5
20
33

score 0 · Answer 2 · answered Dec 27 '17 at 15:07

You're using setTimeOut without creating the promise object, so it's waiting for the setTimeOut value to be returned (which is instant) rather than waiting for a promise resolution. This is the reason your await statement isn't working the way it was intended to. What you need is to create a promise:

function resolveAfterOneSecond(x) { 
  return new Promise(resolve => {
    setTimeout(() => {
      console.log("Middle");
      resolve(x);
    }, 1000);
  });
}

async function f1() {
  var x = await resolveAfterOneSecond(10);
  console.log("End");
}

console.log("Begin");
f1();

and then set your function to await the return of the promise, rather than the return of the setTimeOut function integer.

NodeJs - Async/Await inside controller

2 Answers2