Xmlhttprequest Object

function XML_request(func) {

var onreadystatechange= func;
this.method = "GET";
this.get = function(url) {

var request = null;
var state_change = function() {
if (request.readyState==4) {
if (request.status==200) {
onreadystatechange(request);
} else {
return null;
}
}
}

try {
request = new XMLHttpRequest();
} catch(e) {
try {
request = new ActiveXObject("Microsoft.XMLHTTP");
} catch(e) {
return null;
}
}
if (request===null) {
return null;
}
request.onreadystatechange = state_change;
request.open(this.method, url, true);
request.send(null);
}
}
var req = new XML_request(function(response) {
response = response.responseXML
alert(response.getElementsByTagName('blah')[0].firstChild.data);
});

req.get('index.php?mode=blah&a=response')



i didn't like the examples I found so this is suitable.. I only tested in ie and firefox though.. so let me know what I may be missing.. or criticism in general.