Stopping a timer in JavaScript

You already know how to start a timer, now let's learn how to stop it. To do this, you need to know that each timer started with the setInterval function has a unique number. This number is returned by the setInterval function when the timer starts:

javascriptlet timerId = setInterval(function() {
  console.log('!')
}, 1000);

alert(timerId); // will display the number of the timer

To stop the timer, use the clearInterval function, which takes a unique number of the timer to be stopped.

For example, let's start a timer that prints numbers to the console in ascending order, starting with 1. Let's stop the timer as soon as the number 10 is displayed on the screen:

javascriptlet i = 0;

let timerId = setInterval(function() {
  console.log(++i);
  
  if (i >= 10) {
    clearInterval(timerId);
  }
}, 1000);