JavaScript: setTimeout Memory Leak Prevention.

setTimeout-mem-leak.js

// https://developer.mozilla.org/en-US/docs/Web/API/window.setTimeout

var timeoutID;
delayedAlert();

function delayedAlert() {
  timeoutID = window.setTimeout(slowAlert, 2000);
}

function slowAlert() {
  alert("That was really slow!");
  clearAlert();
}

function clearAlert() {
  window.clearTimeout(timeoutID);
}