Create forms based on previous selection

<?php /*See http://www.javascriptkit.com/script/script2/triplecombo.shtml */ ?>



<script type="text/javascript">

var categories = [];
categories["startList"] = ["Wearing Apparel","Books"]
categories["Wearing Apparel"] = ["Men","Women","Children"];
categories["Books"] = ["Biography","Fiction","Nonfiction"];
categories["Men"] = ["Shirts","Ties","Belts","Hats"];
categories["Women"] = ["Blouses","Skirts","Scarves", "Hats"];
categories["Children"] = ["Shorts", "Socks", "Coats", "Nightwear"];
categories["Biography"] = ["Contemporay","Historical","Other"];
categories["Fiction"] = ["Science Fiction","Romance", "Thrillers", "Crime"];
categories["Nonfiction"] = ["How-To","Travel","Cookbooks", "Old Churches"];

var nLists = 3; // number of select lists in the set

function fillSelect(currCat,currList){
    var step = Number(currList.name.replace(/\D/g,""));
    for (i=step; i<nLists+1; i++) {
        document.forms['tripleplay']['List'+i].length = 1;
        document.forms['tripleplay']['List'+i].selectedIndex = 0;
    }
    var nCat = categories[currCat];
    for (each in nCat) {
        var nOption = document.createElement('option');
        var nData = document.createTextNode(nCat[each]);
        nOption.setAttribute('value',nCat[each]);
        nOption.appendChild(nData);
        currList.appendChild(nOption);
    }
}

function getValue(L3, L2, L1) {
    alert("Your selection was:- \n" + L1 + "\n" + L2 + "\n" + L3);
}

function init() {
    fillSelect('startList',document.forms['tripleplay']['List1'])
}

navigator.appName == "Microsoft Internet Explorer" ? attachEvent('onload', init, false) : addEventListener('load', init, false);

</script>

<form name="tripleplay" action="">
<select name='List1' onchange="fillSelect(this.value,this.form['List2'])">
    <option selected>Make a selection</option>
</select>
&nbsp;
<select name='List2' onchange="fillSelect(this.value,this.form['List3'])">
    <option selected>Make a selection</option>
</select>
&nbsp;
<select name='List3' onchange="getValue(this.value, this.form['List2'].value, this.form['List1'].value)">
    <option selected >Make a selection</option>
</select>
</form>