Do multiple drop-down lists?

How do I make a drop-down list of provinces?

1 Get the Select object var selprov=getel ("Prov");//Get Object

2, traverse the Select Object selprov.options[n]=opt;

3, get the Province object

var prov=new Array (2);
prov["Shaanxi"]=["Xi ' an", "Weinan", "Xianyang", "Hanzhong"];
prov["Henan"]=["Zhengzhou", "Luoyang", "Kaifeng"];
prov["Sichuan"]=["Chengdu", "Guangyuan"];

4, Traverse Province object

For (var p in Prov) {
var opt=new option (P);//Create an Option object
selprov.options[n]=opt;
n++;

How do I get a drop-down list of cities?

1 Get the Select object var selcity=getel ("City")

2, traverse the Select Object selcity.options[i]=opt;

3, get the City object var citys=prov[p];

4, traverse the city object

for (Var i=0;i<citys.length;i++) {
var opt=new Option (Citys[i]);
selcity.options[i]=opt;
}

All code:

<select id= "Prov" onchange= "selcity (this);" >
</select> Province
<select id= "City" ></select>
<script>
var prov=new Array (2);
prov["Shaanxi"]=["Xi ' an", "Weinan", "Xianyang", "Hanzhong"];
prov["Henan"]=["Zhengzhou", "Luoyang", "Kaifeng"];
prov["Sichuan"]=["Chengdu", "Guangyuan"];

function Getel (ID) {
return document.getElementById (ID);
}

Initialize Province
function Initprov () {
var Selprov=getel ("Prov");//Get Object
var n=0;
For (var p in Prov) {
var opt=new option (P);//Create an Option object
selprov.options[n]=opt;
n++;
}
Selcity (Selprov);
}

function Selcity (o) {
var P=o.value;
var citys=prov[p];
var Selcity=getel ("City");//Get HTML Object
Clear
selcity.options.length=0;

for (Var i=0;i<citys.length;i++) {
var opt=new Option (Citys[i]);
selcity.options[i]=opt;
}
}


Initprov ();
</script>
</body>

Do multiple drop-down lists?