Ajax OOP, fejler

Request: function(url, callback)
    {
        this.transport = new Ajax.XMLHttp();
        this.transport.open('GET', url, true);
        this.transport.onreadystatechange = function() {
            callback(this.transport.responseText + ' - ABE');
        }
    }

new Ajax.Request('index.php?ajax', function(jtest) {
    for (var property in jtest) {    document.writeln ("\n " + property + ": " + jtest[property] + "<br>"); }
});

function $(element) { return document.getElementById(element); };
/* Ajax.Request */

var Ajax = {
    GetRequest: function()
    {
        return (window.XMLHttpRequest) ? new XMLHttpRequest() : new ActiveXObject('Microsoft.XMLHTTP');
    },

    Request: function(requestUrl)
    {
        this.transport = new Ajax.GetRequest();
        this.transport.open('GET', requestUrl, true);
        this.transport.onreadystatechange = this.responseData;
        this.transport.send(null);
    },
   
    responseData: function()
    {
        if(this.transport.readyState == 4)
        {
            alert( this.transport.responseText );
        }
    }
   
}
var jtest = new Ajax.Request('index.php?ajax');

for (var property in jtest) { document.writeln ("\n " + property + ": " + jtest[property] + "<br>"); }

function $(element) { return document.getElementById(element); };
/* Ajax.Request */

var Ajax = {
    GetRequest: function()
    {
        return (window.XMLHttpRequest) ? new XMLHttpRequest() : new ActiveXObject('Microsoft.XMLHTTP');
    },

    Request: function(requestUrl, element)
    {
        this.transport = new Ajax.GetRequest();
        this.transport.open('GET', requestUrl, false);
        this.transport.send(null);
        alert( this.transport.responseText );
    }

}
new Ajax.Request('index.php?ajax');