Calculate idle time for webpage using JavaScript

<html>
<head>
<script>
var iddletine = 0;
var timelimit = 15;
var timeinterval = "";
document.onclick = function () {
   console.log(iddletine);
   iddletine = 0;
}
document.onkeyup = function () {
   console.log(iddletine);
   iddletine = 0;
}
function CheckIddle() {
   timeinterval = setInterval(function () {
      iddletine += 1;
      console.log(iddletine);
      if (iddletine == timelimit) {
         clearInterval(timeinterval);
         alert("Session expired, Time limit exceed " + timelimit + " sec");
      }
   },1000);
}
CheckIddle();
</script>
</head>
<body>

</body>
</html>