javascript 实现二级级联菜单，请问！

javascript 实现二级级联菜单，请教！！
请问   javascript   如何实现二级级联菜单？？
用数组？？哪位能给个好点的例子，谢谢
另外js如何取得上一个画面request里边的值？？

------解决方案--------------------
<script type= "text/javascript ">
var CSelect = new Function( "this.initialize.apply(this, Array.apply(null, arguments)) ");

CSelect.prototype = {

initialize : function (a, b) {
var wc = this;
wc.array = [];
wc.select = b;
a.onchange = function () {
var me = this;
wc.change.call(wc, me.options[me.selectedIndex].value);
};
},

change : function (a) {
var wc = this, array = wc.array, o = wc.select, i;
o.options.length = 1;
for (i = 0 ; i < array.length ; i ++) {
if (array[i][0].toString() === a)
o.options[o.options.length] = new Option(array[i][2], array[i][1]);
}
},

add : function (a, b, c) {
//a 为大类ID，b为小类ID，c为小类内容
var wc = this, array = wc.array;
array[array.length] = [a, b, c];
}

};
</script>

<select id= "SortId ">
<option value= " "> 选择大类 </option>
<option value= "0 "> 搜索引擎 </option>
</select>

<select id= "TypeId ">
<option value= " " selected= "selected "> 选择小类 </option>
</select>

<script type= "text/javascript ">
(function () {
var wc = new CSelect(document.getElementById( "SortId "), document.getElementById( "TypeId "));
//ASP便利这里即可。
wc.add(0, 0, "百度 ");
wc.add(0, 1, "google ");
wc = null;
})();
</script>
^o^