JavaScript处理xmlhttprequest返回的xml文档

<script type="text/javascript" language="javascript">
// 修改自 AJAX: Getting Started - MDC
function makeRequest(url) {
var http_request = false;

if (window.XMLHttpRequest) { // Mozilla, Safari,...
http_request = new XMLHttpRequest();
} else if (window.ActiveXObject) { // IE
try {
http_request = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
http_request = new ActiveXObject("Microsoft.XMLHTTP");
} catch (e) {}
}
}

if (!http_request) {
alert('Giving up :( Cannot create an XMLHTTP instance');
return false;
}
// 定義事件處理函數為 alterContents()
http_request.onreadystatechange = function() {
alertContents(http_request); };
http_request.open('GET', url, true);
http_request.send(null);
}

function alertContents(http_request) {
if (http_request.readyState == 4) {
if (http_request.status == 200) {
var xmldoc = http_request.responseXML;//如果返回文本用：responseText
var nodes = xmldoc.getElementsByTagName('area');
var mesg = "";
for(var i=0; i<nodes.length; i++) {
mesg += nodes[i].firstChild.nodeValue + "\n";
}
//alert(mesg);
document.getElementById("taichung").innerHTML = mesg;
} else {
alert('There was a problem with the request.');
}
}
}
</script>