set condition if height more than screen
HTML
<div></div>
CSS
html, body { 0px; 100%; }
div { height: 10px; width: 10px; background: #333;}
.red{ background: red; }
JavaScript
var div = $("div").height();
var doc = $(window).height();
if (div > doc ) {
$("div").addClass('red');
}