Set and clear interval conditionally

Question

I want to stop interval after it reaches 0, but it goes on and on...

here is my code

function timer() {
  var health = 100;
  var counter = 0;
  if (health > 0) {
    counter = setInterval(function () {
      reduce = Math.floor(Math.random() * 15);
      health = health - reduce;
      console.log(health);
    }, 1000);
  } else {
    clearInterval(counter);
  }
}

Answer 1

Do the check and conditional clearInterval inside the scheduled function:

function timer() {
  var health = 100;
  var counter = setInterval(function () {
   var reduce = Math.floor(Math.random() * 15);
   health = health - reduce;
   console.log(health);
   if (health < 0) {
     clearInterval(counter);
   } 
  }, 1000);
}