Syncing the sample code with Promise, await and await

Question

I am learning promises in Node JS. I came across a certain code which I want to synchronize it (Out of Curiousity).

function test1(){
  return new Promise(async function(resolve,reject){
      await promise1();
      await promise2();
      await promise3();
      console.log('last');
      resolve(true);
  })

}

async function promise1(){
  return new Promise(async function(resolve,reject){
      console.log('promise1');
      await setTimeout(myFunc, 1500, resolve);
      console.log("111");
  });
}

function myFunc(resolve) {
  console.log(`arg was => resolve`);
  resolve(true);
}

function promise2(){
  return new Promise(function(resolve,reject){
      console.log('promise2');
      resolve(true);
  });
}

function promise3(){
  return new Promise(function(resolve,reject){
      console.log('promise3');
      resolve(true);
  });
}

function callTest1(){
  for(i=0;i<4;i++){
    test1();
  }
}

callTest1();

I want the output like this :

promise1
arg was => resolve
111
promise2
promise3
last
promise1
arg was => resolve
111
promise2
promise3
last
promise1
arg was => resolve
111
promise2
promise3
last
promise1
arg was => resolve
111
promise2
promise3
last

I want my code to wait for setTimeOut and then after only it should run other function. I know, in node js we have concept of Asynchronization But somehow I want this code to be sync.

Possible duplicate of [Synchronous request in Node.js](https://stackoverflow.com/questions/6048504/synchronous-request-in-node-js) — dr0i, Dec 17 '18 at 16:16
Never ever pass an `async function` as a callback to `new Promise`! — Bergi, Dec 17 '18 at 18:38

score 0 · Answer 1 · answered Dec 17 '18 at 15:40

A key rule in node.js is that it is impossible to synchronize asynchronous code.

You can easily obtain your desired result by making callTest itself asynchronous, for example:

async function callTest1() {
  for(i=0;i<4;i++){
    await test1();
  }
}

Now your output will appear as desired, but of course the call to callTest1() will return immediately (and the output will print afterwards).

Syncing the sample code with Promise, await and await

1 Answers1