<script type="application/javascript">

//二维数组存放市的信息

var shi =[["丽水市","杭州市"],["新乡","郑州"]];

//三维数组存放县的信息

var xianes = [[["云和","景宁"],["桐庐","原阳"]],[["卫辉","下乡"],["中原","二七"]]];

//所选的省值

var proIndex = 0;

function sgc(){

//获得所选择的省的下拉框值

var pro = document.getElementById("sheng");

//获得市的下拉框

var cit = document.getElementById("shi");

//将省的value与市的一维数组下标所对应

proIndex = pro.value-1;

//清空市下拉框中原有的值

cit.options.length = 1;

//通过for循环往下拉框中添加市的信息

for(var i = 0;i < shi[proIndex].length;i++){

var op = document.createElement("option");

var citName = document.createTextNode(shi[proIndex][i]);

op.value = i;

op.appendChild(citName);

cit.appendChild(op);

}

}

//市的值改变后改变县的值

function sic(){

var are = document.getElementById("xian");

var cit = document.getElementById("shi");

are.options.length = 1;

//通过proIndex获得所选的省的值作为县的数组的一维数组下标，通过cit.value作为县数组的二维数组下标，遍历获得数组值

for(var i = 0;i<xianes[proIndex][cit.value].length;i++){

var op = document.createElement("option");

var areName = document.createTextNode(xianes[proIndex][cit.value][i]);

op.value = i;

op.appendChild(areName);

are.appendChild(op);

}

}

</script>

//onchange():控件的value值改变后调用方法

<select id = "sheng" onchange = "sgc();">

<option>----省份---</option>

<option value = "1">浙江省</option>

<option value = "2">河南省</option>

</select>

<select id = "shi" onchange="sic();">

<option>---市区---</option>

</select>

<select id = "xian" >

<option>---县区---</option>

</select>