what does cleartimeout return code example

Example 1: js cleartimeout

var myVar;

function myFunction() {
  myVar = setTimeout(function(){ alert("Hello"); }, 3000);
}

function myStopFunction() {
  clearTimeout(myVar);
}

Example 2: clear timeout in function js

var timer;
function endAndStartTimer() {
  window.clearTimeout(timer);
  var millisecBeforeRedirect = 10000; 
  timer = window.setTimeout(function() {
    alert('Hello!');
  }, millisecBeforeRedirect); 
}