JQuery实现二级 select框联动选择

jQuery版本：1.2.6 
 

<!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 runat="server">
    <title>无标题页</title>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <script type="text/javascript" src="jquery.js"></script>
    <style type="text/css">
        .sub{display:none;}
    </style>
</head>
<body>
    <select id="sel1">
        <option>北京</option>
        <option>安徽省</option>
    </select>
    <select class="sub">
        <option>中关村</option>
        <option>朝阳区</option>
    </select>    
    <select class="sub">
        <option>合肥</option>
        <option>安庆</option>
    </select>
    <script type="text/javascript">
        $(document).ready(function(){
            $("#sel1").change(function(){
                $("#sel1 option").each(function(i,o){
                    if($(this).attr("selected"))
                    {
                        $(".sub").hide();
                        $(".sub").eq(i).show();
                    }
                });
            });
            $("#sel1").change();
        });
    </script>
</body>
</html>