jQuery trigger function when element is in viewport

<!DOCTYPE html>
<html>
<head>
<title>jQuery Demo example</title>
<script type="text/javascript" src="http://code.jquery.com/jquery-2.1.4.min.js">
 </script>
<script type="text/javascript">
function isIntoView(elem)
{
    var documentViewTop = $(window).scrollTop();
    var documentViewBottom = documentViewTop + $(window).height();

    var elementTop = $(elem).offset().top;
    var elementBottom = elementTop + $(elem).height();

    return ((elementBottom <= documentViewBottom) && (elementTop >= documentViewTop));
}
  $(window).scroll(function(){
   if (isIntoView($('#myDiv'))){
       alert("Div in view port");
    }
})
</script>
 </head>	
<body>
<div id="myDiv" style="margin-top:500px;width:200px;height:200px;background:yellow;">
<h2>Demo Div</h2>
</div> 
</body>
</html>