Why Promise is not displaying the data with setTimeout?

Question

I wrote a function to get a random number after 500 milliseconds and it worked perfectly with (return new Promise (resolve,reject)), also, it worked without it by using setTimeout() function, but when I added the promise and setTimeout() inside it wont show the result, I have console.log() before and after the result and both are showing. Please note that i am still new to the promise concept in general since this is a task from my coding school, thank you.

My code:

function getRandomNumber () {
   new Promise ((resolve,reject) =>{
      console.log('Getting Random Number...');
      let number =   Math.random();
      setTimeout( () => {
         if(number){
            resolve (`OK ${number}`);
            console.log('Done!');
         }
         else
            reject ('ERROR');
      }, 500);
   });   
 }
    
getRandomNumber();

Result:

Answer 1

First, return your promise, second use the result the promise provides either by creating a variable from it and awaiting it or using then

function getRandomNumber() {
    return new Promise((resolve, reject) => {
        console.log('Getting Random Number...');
        let number = Math.random();
        setTimeout(() => {
            if (number) {
                resolve(`OK ${number}`);
                console.log('Done!');
            } else {
                reject('ERROR');
            }
        }, 500);
    });

}

getRandomNumber().then(result => console.log(result));

(async () => {
  const number = await getRandomNumber();
  console.log(number);
 })();

Another option is to write sleep as a separate reusable function. Note async function can await multiple values and return values of their own. Calling an async function will always return a Promise -

function sleep(time) {
  return new Promise(resolve => setTimeout(resolve, time))
}

async function getRandomNumber() {
  console.log('Getting Random Number...')
  await sleep(500)
  const number = Math.random()
  console.log("Done!")
  return number
}

async function main() {
  const number1 = await getRandomNumber()
  console.log("number1", number1)
  const number2 = await getRandomNumber()
  console.log("number1", number2)
  const number3 = await getRandomNumber()
  console.log("number1", number3)
  return number1 + number2 + number3
}

main().then(console.log, console.error)

.as-console-wrapper { min-height: 100%; }

Getting Random Number...
Done!
number1 0.2907058138817884
Getting Random Number...
Done!
number1 0.05784624607512423
Getting Random Number...
Done!
number1 0.889702848981964
1.2382549089388766