js的2级联动的一种方法！

 <script language="JavaScript" type="text/javascript">
var arrlist1=new Array(3)
arrlist1[0]=new Array("111","111的只");
arrlist1[1]=new Array("111","111111");
arrlist1[2]=new Array("111","11111");
var arrlist2=new Array(3)
arrlist2[0]=new Array("22222","2222");
arrlist2[1]=new Array("222222","222");
arrlist2[2]=new Array("22222","222");

function changlist(obj){
var arrlistid=obj.value
var arrlist=eval("arrlist"+arrlistid)
//alert(arrlist)
var obj=document.getElementById("b");
//obj.options.length=0;
for (i=0;i<arrlist.length;i++){
obj.options[i]=new Option(arrlist[i][0],arrlist[i][1])
}
}
</script>

<form id="form1" name="form1" method="post" action="">
<select name="a" id="a" onchange="changlist(this)">
  <option value="2">&gt;&gt;留学</option>
  <option value="1">&gt;&gt;移民</option>
</select>
<select name="b" id="b">
  <option>请选择</option>
</select>
</form>