jQuery兑现侧边栏随窗口滚动

jQuery实现侧边栏随窗口滚动

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<script type="text/javascript" src="js/jquery-1.4.2.min.js"></script>
<script type="text/javascript">   
$(function() {
    var $sidebar   = $("#sidebar"),   
        $window    = $(window),   
        offset     = $sidebar.offset(),   
        topPadding = 15;   
  
    $window.scroll(function() {   
        if ($window.scrollTop() > offset.top) {   
            $sidebar.stop().animate({   
                marginTop: $window.scrollTop() - offset.top + topPadding   
            });   
        } else {   
            $sidebar.stop().animate({   
                marginTop: 0   
            });   
        }   
    });   
  
});   
</script>  
</head>

<body>
<div style="width:300px; float:left; height:2500px; background:#930;"></div>
<div id="sidebar" style="width:300px; float:right; height:500px; background:#999;"></div>
</body>
</html>