怎么用easyui创建两个依赖下拉框 省市联动 不走后台

<tr>
<td class="tdlft">所属城市</td>
<td><select id="jia1" onchange="setjia2()"
class="easyui-combobox" name="dept" style="width: 200px">
</select></td>
</tr>
<tr>
<td class="tdlft">所属县</td>
<td><select id="jia2" class="easyui-combobox" name="dept"
style="width: 200px">
</select></td>
<script language="javascript">
var dat = [

["山东","济南","青岛","潍坊","淄博","济宁","烟台"],
["辽宁","沈阳","大连","鞍山","葫芦岛","丹东"],
["北京","东城区","西城区","海淀区","朝阳区","昌平区"],
["上海","黄浦区","宝山区","嘉定区","浦东新区","虹口区"]

];
var jia1 = document.getElementById("jia1");
var jia2 = document.getElementById("jia2");
for(var i=0; i<dat.length; i++){
jia1.add(new Option(dat[i][0]));
}
(function setjia2(){
jia2.length = 0;
var dat2 = dat[jia1.selectedIndex];
for(var i=1; i<dat2.length; i++){
jia2.add(new Option(dat2[i]));
}
})();
</script>
</tr>

省一个数组、市是二维数组、区是另一个二维数组

省点击后，显示对应的市的

市选中后，显示对应的区的

先用类似httpwatch的工具，看看服务器有没有返回正确的数据。然后再排查是不是前端绑定出了问题