อยากทำความเข้าใจใน ajax framework ka พอดีทำโปรเจคโดยใช้ajax อ่ะค่ะ

method = method.toLowerCase();
	URL += "?dummy=" + (new Date()).getTime();
	if(method=="get") {
		URL += "&" + data;
		data = null;
	}

	ajax.open(method, URL);

	if(method=="post") {
		ajax.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
	}
	
	ajax.onreadystatechange = function() {
		if(ajax.readyState==4 && ajax.status==200) {
			var ctype = ajax.getResponseHeader("Content-Type").toLowerCase();
			ajaxCallback(ctype, displayId, ajax.responseText);

			delete ajax;
			ajax = null;
		}
	}

	ajax.send(data);
}