Why this easy settimeout doesn't work?

Why this easy settimeout doesn't work?

[Question] Why does this alert message show up even after the full page is loaded within 3 seconds?


<!DOCTYPE >
<html>
 <head>
  <script type="text/javascript">
    var slowLoad = window.setTimeout( function() {
        alert( "This page took 5 seconds or more.");
    }, 5000);

    document.addEventListener( 'load', function() {
        window.clearTimeout( slowLoad );
    }, false );
</script>
 </head>
 <body>

Your downloading will not take 5 seconds or more.

</body>

</html></dob