Mine

function AjaxWorker(remoteTarget, requestHandler) {
	this.sendRequest = sendRequest;
	this.createRequestObject = createRequestObject;

	this.remoteTarget = remoteTarget;
	this.requestHandler = requestHandler;
	this.http = createRequestObject();
}

function createRequestObject() {
	if (navigator.appName == "Microsoft Internet Explorer") {
		return new ActiveXObject("Microsoft.XMLHTTP");
	} else {
		return new XMLHttpRequest();
	}
}

function sendRequest(reqParams) {
	this.http.open('get', this.remoteTarget + "?" + reqParams);
	this.http.onreadystatechange = requestHandler;
	this.http.send(null);
}