<script type="text/javascript">
var xmlHttp;
var requestType="";

function createXMLHttpRequest()
{
if(window.ActiveXObject)
{
xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
}
else if(window.XMLHttpRequest)
{
xmlHttp=new XMLHttpRequest();
}
if(!xmlHttp)
{
alert("创建ajax对象实例失败!");
}
}

function startRequest(requestedList)
{
requestType=requestedList;
createXMLHttpRequest();
xmlHttp.onreadystatechange=handleStateChange;
xmlHttp.open("POST","states.xml",true);
xmlHttp.send(null);
}
function handleStateChange()
{
if(xmlHttp.readyState==4)
{
if(xmlHttp.status==200)
{
if (requestType=="north")
{
ListNorthStates()
}
else if(requestType=="all")
{
listAllStates()
}
}
}
}
function ListNorthStates()
{
var xmlDoc=xmlHttp.responseXMl;
var northNode=xmlDoc.getElementsByTagName("north")[0];
var out="Northern States";
var northStates=northNode.getElementsByTagName("state");
outputList("Northern States",northStates);
}
function listAllStates()
{
var xmlDoc=xmlHttp.responseXMl;
var allStates=xmlDoc.getElementsByTagName("state");
outputList("All States in Document",allstates);
}
function outputList(title,states)
{
var out=title;
var currentState=null;
for(var i=0;i<states.length;i++)
{
currentState=states[i];
out=out+"\n-"+currentState.childNodes[0].nodeValue;
}
alert(out);
}
</script>