How do I achieve my requirement of synchronus execution in Node.js

Question

I've a requirement where I have to call another function for a record of data before I actually perform next set of operations.

so here's what I'm doing but it doesn't work. function a is stored in a common library abc

var a = (req,callBack) =>{
DB Operation
.
.
.
.
callBack(null,result);
}

var b = (req,callBack) =>{
const c = await abc.a(req,response);
DB Operation
.
.
.
.
.
callBack(null,result);
}

when I do const c = await abc.a(req,response); it gives me error "await is only valid in async function" but I've seen examples where await is used like this.

can you please help me with this.

I think the error message is somewhat self-explanatory... is it not? [Possible duplicate](https://stackoverflow.com/q/49432579/1541563) — Patrick Roberts, Oct 16 '19 at 05:03
_"but I've seen examples where await is used like this"_ - Then you've missed the `async` in the examples — Andreas, Oct 16 '19 at 05:03

shubham-gupta · Answer 1 · 2019-10-16T05:23:51.287

1

You are not using async/await properly. Await only works inside async functions. So make your function async.

var b = async (req,callBack) =>{ // made this function async
    abc.a(req, (_, res) => {
        DB Operation
        .
        .
        .
        .
        .
        callBack(null,result);
    });
}

edited Oct 16 '19 at 05:23

answered Oct 16 '19 at 05:07

shubham-gupta

208
1
5

That dint help it gives a warning 'await' has no effect on the type of this expression. and when I test it it doesnt wait for response. – Nick Oct 16 '19 at 05:16
If function a which is a library function returns a callback. Then you don't need to use async/await. You can just have your data in callback response. – shubham-gupta Oct 16 '19 at 05:22

score 0 · Answer 2 · answered Oct 16 '19 at 05:45

0

You'r code would like.

async function a () {
  const b = await funcX()
}

or

const b =  async () => {
  const b = await funcX()
}

like that

answered Oct 16 '19 at 05:45

ucode

31
1
1
5

score 0 · Answer 3 · answered Oct 16 '19 at 06:08

await is only valid if the called function returns a promise, or is marked async.

Furthermore, await must be used from within an async function.

Both are false in your case.

Don't use async/await...

var b = (req,callBack) =>{
 abc.a(req,c=>{
  DB Operation
  callBack(null,result);
 });
}

You can wrap your functions inside async functions if you insist on using that syntax.

How do I achieve my requirement of synchronus execution in Node.js

3 Answers3