Losing object reference in Javascript with await

June 13, 2022

I was learning the event loop of Js and tried to run this function:

async function foo() {
    console.log('FIrst');
    let a = await new Promise((resolve,reject)=>{
        console.log("inside Promise");
        resolve();
    })
    console.log(a);
    console.log('Second');
} 
foo();
console.log('Three');

On running this code gave output as follows:

FIrst
inside Promise
Three
undefined
Second

I am not able to understand why did a lose its value (the object assignment). I have searched for this behavior but was not able to understand from the answers.
Can someone please explain what is the order of execution which results in this output.

>Solution :

When you await the newly created promise, you’re not assigning the promise to a, you’re assigning the resolve value of it.

async function foo() {
    let a = await new Promise((resolve, reject) => {
        // This is where the value stems from
        resolve(42);
    });
    console.log(a);
} 
foo();

If you want to keep the await while also retrieving the reference, you can separate those two steps:

async function foo() {
    let a = new Promise((resolve, reject) => {
        resolve(42);
    });
    await a;
    console.log(a instanceof Promise);
} 
foo();