Generic AJAX Object

Posting a code that you can use in your page to implement AJAX. Its is not a full fleged javascript object yet, but I feel its good enough to start.

function ajaxcore(){
 var req;  //  the request object
 var cbfn; // name of the callback function

 this.initRequest = function(){
  if (window.XMLHttpRequest) {
   req = new XMLHttpRequest();
  }
  else if (window.ActiveXObject) {
   req = new ActiveXObject("Microsoft.XMLHTTP");
  }
  else {
   throw new Error("XMLHttpRequest not supported");
  }
 }

// Call this method for processing your request.
// arguments:
//  cbFunName - name of callback function that you will handle
//  url - servlet URL
// todo..
// provide additional argument that would be a 
// form object which would be parsed
//   and then given to the server for processing.
 this.doCompletion = function(url,cbFunName) {
  if ("undefined" == cbFunName){
   alert ("Inappropriate Callback function specified. Aborting server 
    call without further action.");
   return;
  }
  cbfn = cbFunName   function () { };

  try{
   this.initRequest();
  }
  catch (e){
   alert ("Unable to create XML request object.")
  }

  if (req != null){
   req.onreadystatechange = function() {
    if (null != req ){
     if (req.readyState == 4){
      cbfn (req.responseText,req.responseXML,req.readyState,req);
     }else {
      cbfn (null,null,req.readyState,req);
     }

    }
    else{
     //todo...
    }
   }
   req.open("GET", url, true);
   req.send(null);
  }
  else{
   alert ("You are probably using a primitive browser.");
  }
 }
}// Main End