在js中如何实现二级联动

<script language="javascript" type="text/javascript">
 //定义 费用科目 数据数组
 fylxArray = new Array();
 fylxArray[0] = new Array("","");
 fylxArray[1] = new Array("汽车费用","汽油费|过路费|修理费");
 fylxArray[2] = new Array("房屋租赁费","分公司及办事处房租|宿舍房租|项目房租");
 fylxArray[3] = new Array("差旅费用","餐费|住宿费|交通费");
 fylxArray[4] = new Array("招待费","招待费");
 fylxArray[5] = new Array("办公费","办公用品费|办公费");
 fylxArray[6] = new Array("交通费","交通费");
 fylxArray[7] = new Array("物业费","物业费");
 fylxArray[8] = new Array("租车费","租车费");
 fylxArray[9] = new Array("劳务费","劳务费");
 fylxArray[10] = new Array("通讯费","通讯费");
 fylxArray[11] = new Array("水费","水费");
 fylxArray[12] = new Array("电费","电费|职工福利费");
 fylxArray[13] = new Array("会议费","会议费");
 fylxArray[14] = new Array("中介服务费","审计费|律师费|券商费|其他");
 fylxArray[15] = new Array("快递费","快递费");
 fylxArray[16] = new Array("招聘费","招聘费");
 fylxArray[17] = new Array("加班餐费","加班餐费");
 fylxArray[18] = new Array("投标费用","投标报名费|购买标书费");
 fylxArray[19] = new Array("打印装订费","打印费|装订费|文件制作费");
 fylxArray[20] = new Array("广告宣传费","展位费|广告费|设计费|印刷费");
 fylxArray[21] = new Array("中标服务费","中标服务费");
 fylxArray[22] = new Array("专家咨询费","专家咨询费");
 fylxArray[23] = new Array("培训费","培训费");
 fylxArray[24] = new Array("打印费","打印费");
 fylxArray[25] = new Array("职工福利费","职工福利费");
 fylxArray[26] = new Array("暖气费","暖气费");
 fylxArray[27] = new Array("燃气费","燃气费");
 fylxArray[28] = new Array("产检费","产检费");
 fylxArray[29] = new Array("生育住院费","生育住院费");
 fylxArray[30] = new Array("生育津贴","生育津贴");
 fylxArray[31] = new Array("医疗保险费","医疗保险费");
 fylxArray[32] = new Array("其他","其他");
 //select 二级联动
 function getChild(currFylx){
 //当前 所选择 的费用类型
 var currFylx_value = currFylx.options[currFylx.selectedIndex].value;
 var currFylxid=currFylx.id.substr(0,6)
 //清空 费用科目 下拉选单
 //var currOption= document.getElementById(currFylxid+'_fykm')
 var currOption= $(currFylx).parent().next().children()[0]
 currOption.length=0
 for (var i = 0 ;i <fylxArray.length;i++){
 //得到 当前费用类型 在 费用科目数组中的位置
 if(fylxArray[i][0]==currFylx_value){
 //得到 当前费用类型 下的费用科目
 var tmpfykmArray = fylxArray[i][1].split("|")
 for(var j=0;j<tmpfykmArray.length;j++){
 //填充 费用科目 下拉选单
 currOption.options[currOption.length] = new Option(tmpfykmArray[j],tmpfykmArray[j]);
 }
 } 
 }
 }
</script>

<td class="ff"><select style="width:100px" name="select_name" onChange = "getChild(this)">
<option value="">--无--</option>
<option value="汽车费用">汽车费用</option>
<option value="房屋租赁费">房屋租赁费</option>
<option value="差旅费用">差旅费用</option>
<option value="招待费">招待费</option>
<option value="办公费">办公费</option>
<option value="交通费">交通费</option>
<option value="物业费">物业费</option>
<option value="租车费">租车费</option>
<option value="劳务费">劳务费</option>
<option value="通讯费">通讯费</option>
<option value="水费">水费</option>
<option value="电费">电费</option>
<option value="会议费">会议费</option>
<option value="中介服务费">中介服务费</option>
<option value="快递费">快递费</option>
<option value="招聘费">招聘费</option>
<option value="加班餐费">加班餐费</option>
<option value="投标费用">投标费用</option>
<option value="打印装订费">打印装订费</option>
<option value="广告宣传费">广告宣传费</option>
<option value="中标服务费">中标服务费</option>
<option value="专家咨询费">专家咨询费</option>
<option value="培训费">培训费</option>
<option value="打印费">打印费</option>
<option value="职工福利费">职工福利费</option>
<option value="暖气费">暖气费</option>
<option value="燃气费">燃气费</option>
<option value="产检费">产检费</option>
<option value="生育住院费">生育住院费</option>
<option value="生育津贴">生育津贴</option>
<option value="医疗保险费">医疗保险费</option>
<option value="其他">其他</option>
</select></td><!--费用类型-->
<td class="ff"><select style="width:100px" ><option>--无--</option></select></td><!--费用科目-->