Trigger JavaScript on Active Browser Window or Tab

Following code triggers JavaScript on active browser window or tab:

<script src="http://code.jquery.com/jquery-1.7.1.min.js"></script>
<script>

	function callOnFocus() {
		alert('Alerts after one second of window or tab focus!');
	}

	var interval_id;
	$(window).focus(function() {
	    if (!interval_id)
	        interval_id = setInterval(callOnFocus, 1000);
	});

	$(window).blur(function() {
		// alert('On blur test');
	    clearInterval(interval_id);
	    interval_id = 0;
	});
	  
</script>