clearInterval() doesn't work and I can't figure out why

Question

I'm trying to add play/pause button to a timer with a function that decides what to do based on the value of isRunning. When clicked second time my button instead of pausing, timer adds another setTimeout it seems and I can't figure out why.

var isRunning = false;

function start() {
  if(isRunning == false) {
    isRunning = true;
    setInterval(time, 1000);
    document.getElementById("play").className = "fa fa-pause";
  } 
  else if(isRunning == true) {
    isRunning = false;
    document.getElementById("play").className = "fa fa-play";
    console.log(isRunning);
    clearInterval(time);
  }
}

document.getElementById("play").onclick = start;

Answer 1

var isRunning = false;
var timeoutId; // Where the timeout id will be stored.

function start() {
  if(isRunning == false) {
    isRunning = true;
    timeoutId = setInterval(time, 1000);
    document.getElementById("play").className = "fa fa-pause";
  } 
  else if(isRunning == true) {
    isRunning = false;
    document.getElementById("play").className = "fa fa-play";
    console.log(isRunning);
    clearInterval(timeoutId); // clearInterval using timeout id saved before.
  }
}

document.getElementById("play").onclick = start;

For more information visit https://developer.mozilla.org/es/docs/Web/API/WindowTimers/setTimeout