I've spent several hours to change the color of div background.

My question is How to change background color of div when the div is scroll top ?

Code

2. var docInHeight = jQuery(this).innerHeight;
3.             var obj_div = jQuery('#div');
4.             obj_div.scroll(function () {
5.                 if (jQuery(this).scrollTop() == 0) {
6.                     jQuery(this).css('background', 'red');
7.                 }
8.             })

Thanks in advance