asp 省份、城市、城镇三级联动

<script>
<!--
<%
'二级数据保存到数组
Dim count2,cityRS,citySQL
set cityRS=server.createobject("adodb.recordset")
citySQL="select * from sys_city"
cityRS.open citySQL,conn,1,1
%>
var subval2 = new Array();
//数组结构：一级根值,二级根值,二级显示值
<%
count2 = 0
do while not cityRS.eof
%>
subval2[ <%=count2%>] = new Array(' <%=cityRS("provinceid")%>',' <%=cityRS("id")%>',' <%=cityRS("cityname")%>')
<%
count2 = count2 + 1
cityRS.movenext
loop
cityRS.close
%>
<%
'三级数据保存到数组
Dim count3,townRS,townSQL
set townRS=server.createobject("adodb.recordset")
townSQL="select * from sys_town"
townRS.open townSQL,conn,1,1
%>
var subval3 = new Array();
//数组结构：二级根值,三级根值,三级显示值
<%
count3 = 0
do while not townRS.eof
%>
subval3[ <%=count3%>] = new Array(' <%=townRS("cityid")%>',' <%=townRS("ID")%>',' <%=townRS("townname")%>')
<%
count3 = count3 + 1
townRS.movenext
loop
townRS.close
%>
function changeselect1(locationid)
{
    document.form1.cityID.length = 0;
    document.form1.cityID.options[0] = new Option('请选择城市','');
document.form1.townID.length = 0;
    document.form1.townID.options[0] = new Option('请选择城区','');
    for (i=0; i <subval2.length; i++)
    {
        if (subval2[i][0] == locationid)
        {document.form1.cityID.options[document.form1.cityID.length] = new Option(subval2[i][2],subval2[i][1]);}
    }
}

function changeselect2(locationid)
{
    document.form1.townID.length = 0;
    document.form1.townID.options[0] = new Option('请选择城区','');
    for (i=0; i <subval3.length; i++)
    {
        if (subval3[i][0] == locationid)
        {document.form1.townID.options[document.form1.townID.length] = new Option(subval3[i][2],subval3[i][1]);}
    }
}
//-->
</script>
<form id="form1" name="form1" method="post" action="">
<%
  Dim count1,provinceRS,provinceSQL
  set provinceRS=server.createobject("adodb.recordset")
  provinceSQL="select * from sys_province order by orderfield"
  provinceRS.open provinceSQL,conn,1,1
%>
          <select name="provinceID" id="provinceID" onchange="changeselect1(this.value)">
            <option value="">请选择省份 </option>
            <%
do while not provinceRS.eof
  response.Write " <option value="&provinceRS("ID")&">"&provinceRS("provincename")&" </option>"
provinceRS.movenext
loop
provinceRS.close
set provinceRS = nothing
%>
          </select>
          <select name="cityID" id="cityID" onchange="changeselect2(this.value)">
            <option value="">请选择城市 </option>
          </select>
          <select name="townID" id="townID">
            <option value="">请选择城区 </option>
          </select>
</form>