async javascript function issue -

i having problem javascript function callback.

for example have code this:

var base = {      // constructor of class     createnew: function(name) {         var base = {};          base.ajax = function(callback, url) {             // create xmlhttprequest object             var httprequest;             if (window.xmlhttprequest) {                 httprequest = new xmlhttprequest();             } else if (window.activexobject) {                 httprequest = new activexobject("microsoft.xmlhttp");             }              httprequest.onreadystatechange = function() {                 // check status of our request                 // called on every state change                 if (httprequest.readystate == 4 && httprequest.status == 200) {                     // call callback function                     callback.call(httprequest.responsetext);                 }             };              httprequest.open("get", some_url, true);             httprequest.send();         };           return base;     } }; 

and create class inherits base:

var test = {      createnew: function() {          var test = base.createnew();          test.json = {};          test.ajax( function(){             test.json = json.parse( );         });          return test;     } }; 

and create class call mytest inherits test:

// create class 300x250     var mytest = {     createnew: function() {         var mytest = test.createnew();         return mytest;     } };  var mytest = mytest.createnew();  console.log(mytest.json); 

however, when try console.log(mytest.json), can't data. know it's because in test class, json in ajax function, don't know how solve async problem, idea?