set interval inside a function must return resolve message or reject

jonas :

I am trying to make a timer, and trying to exit from the callback hell that is happening inside the code I am writing, this is a part from the code I have written, the problem is that I am not receiving the feedback from the promise, so no resolve message, no reject message. what is the problem?

       var timer = 15;

        var startTimer = (timer) => {
            return new Promise((resolve, reject)=>{
               if(resolve){
                var countDown = setInterval(() => {
                    console.log(timer);
                    timer--;
                    if (timer == 0) {
                    clearInterval(countDown);
                    return "YOU ARE LOSER";
                    }
                }, 1000);
               }
               if(reject){
                   return "sorry something went wrong!";
               }
            })
        }

        startTimer(timer)
        .then(message =>{
            console.log(message);
            //the message should be "You are loser!".
        })
        .catch(message =>{
            console.log(message);
        })

Shoejep :

You're using promises wrong, take a look at this friendly tutorial.

You resolve or reject the value that you want to return.

var timer = 15;

var startTimer = (timer) => {
  return new Promise((resolve, reject) => {
    try {
      var countDown = setInterval(() => {
        console.log(timer);
        timer--;
        if (timer == 0) {
          clearInterval(countDown);
          resolve("YOU ARE LOSER");
        }
      }, 1000);
    } catch (err) {
      reject("sorry something went wrong!");
    }
  })
}

startTimer(timer)
  .then(message => {
    console.log(message);
  })
  .catch(message => {
    console.log(message);
  })

Simplified version without promises

var timer = 10;
var countDown = 0;

var startTimer = fn => setInterval(() => {
  console.log(timer);
  if (--timer === 0)
  {
    clearInterval(countDown);
    console.log("You lose");
    if(fn)
    fn();
  }
}, 500);

function onTimerFinished() {
console.log("Timer has finished");
}

try {
  countDown = startTimer(onTimerFinished);
} catch (err) {
  console.error(err);
}