JavaScript实现仿腾讯游戏区服选择功能

<!doctype html>
<html lang="en">
 <head>
 <meta charset="UTF-8">
 <meta name="Generator" content="EditPlus®">
 <meta name="Author" content="">
 <meta name="Keywords" content="">
 <meta name="Description" content="">
 <title>纸牌游戏</title>
 <style type="text/css">
 #div{width:450px;height:134px;border:1px solid #fff}
 </style>
 </head>
 <body>
 <center>
 <div id="div">
 <img src="images/banner.jpg" width="450" height="134" border="0" alt="">
 </div>
 <div style="width:450px;height:134px;border:1px solid #fff;background:#1C85B4">
 <p>请选择游戏类别:<select id="lei" onChange="ck()" >
 <option>--游戏分类--</option>
 </select></p>
  <p>请选择游戏名称:<select id="youxi">
 <option>--游戏名称--</option>
 </select></p>
   <p><input name="" type="image" src="images/login.gif" /></p>
 </div>
 </body>
 <script type="text/javascript">
 var lei= document.getElementById("lei");
 var youxi= document.getElementById("youxi");
 //创建省市数组
 var List=new Array();
   List['纸牌游戏'] = ['斗地主','拖拉机','桥牌','拱猪','打百分'];
   List['棋类游戏'] = ['围棋','象棋','跳棋','西瓜棋','五子棋'];
   List['其他游戏'] = ['枪林弹雨','跑跑卡丁车','英雄联盟','CF','英雄三国'];
   for(var i in List){
    lei.add(new Option(i,i),null);
   }
    lei.onchange=function(){
    var lei= document.getElementById("lei").value;
    var youxi= document.getElementById("youxi");
    youxi.options.length=0;
    for(var k in List[lei]){
       youxi.add(new Option(List[lei][k],List[lei][k]),null);  
  }
 }
</script>
</html>