JS二级联动

<form name="frm">
  <select name="s1" onChange="redirec(document.frm.s1.options.selectedIndex)">
    <option value="0" selected>请选择</option>
    <option value="1">脚本语言</option>
    <option value="2">高级语言</option>
    <option value="3">其他语言</option>
  </select>
  <select name="s2">
 <option value="0" selected>请选择</option>
</select>
</form>

<script language="javascript">
//获取一级菜单长度
var select1_len = document.frm.s1.options.length;
var select2 = new Array(select1_len);

//把一级菜单都设为数组
for (i=0; i<select1_len; i++)
{
 select2[i] = new Array();
}

//定义基本选项
select2[0][0] = new Option("请选择", " ");

select2[1][0] = new Option("PHP", "10");
select2[1][1] = new Option("ASP", "11");
select2[1][2] = new Option("JSP", "12");

select2[2][0] = new Option("C/C++", "20");
select2[2][1] = new Option("Java", "21");
select2[2][2] = new Option("C#", "22");

select2[3][0] = new Option("Perl", "30");
select2[3][1] = new Option("Ruby", "31");
select2[3][2] = new Option("Python", "32");

//联动函数
function redirec(x)
{
 var temp = document.frm.s2;
 for (i=0;i<select2[x].length;i++)
 {
  temp.options[i]=new Option(select2[x][i].text,select2[x][i].value);
 }
 temp.options[0].selected=true;

}
</script>