Javascript Ajax Object (See related posts)

// Just a stub function we'll tell ajaxObject to call when it's done
// callback functions get responseText, and responseStat respectively
// in their arguments.
function fin(responseTxt,responseStat) {
  alert(responseStat+' - '+responseTxt);
}

// create a new ajaxObject, give it a url it will be calling and
// tell it to call the function "fin" when its got data back from the server.
var test1 = new ajaxObject('http://someurl.com/server.cgi',fin);
    test1.update();
		
// create a new ajaxObject, give it a url and tell it to call fin when it
// gets data back from the server.  When we initiate the ajax call we'll
// be passing 'id=user4379' to the server.		
var test2 = new ajaxObject('http://someurl.com/program.php',fin);
    test2.update('id=user4379');
		
// create a new ajaxObject but we'll overwrite the callback function inside
// the object to more tightly bind the object with the response hanlder.
var test3 = new ajaxObject('http://someurl.com/prog.py', fin);
    test3.callback = function (responseTxt, responseStat) {
      // we'll do something to process the data here.
      document.getElementById('someDiv').innerHTML=responseTxt;
    }
    test3.update('coolData=47&userId=user49&log=true');	
		
// create a new ajaxObject and pass the data to the server (in update) as
// a POST method instead of a GET method.
var test4 = new ajaxObject('http://someurl.com/postit.cgi', fin);
    test4.update('coolData=47&userId=user49&log=true','POST');	

function ajaxObject(url, callbackFunction) {
  var that=this;      
  this.updating = false;
  this.abort = function() {
    if (that.updating) {
      that.updating=false;
      that.AJAX.abort();
      that.AJAX=null;
    }
  }
  this.update = function(passData,postMethod) { 
    if (that.updating) { return false; }
    that.AJAX = null;                          
    if (window.XMLHttpRequest) {              
      that.AJAX=new XMLHttpRequest();              
    } else {                                  
      that.AJAX=new ActiveXObject("Microsoft.XMLHTTP");
    }                                             
    if (that.AJAX==null) {                             
      return false;                               
    } else {
      that.AJAX.onreadystatechange = function() {  
        if (that.AJAX.readyState==4) {             
          that.updating=false;                
          that.callback(that.AJAX.responseText,that.AJAX.status,that.AJAX.responseXML);        
          that.AJAX=null;                                         
        }                                                      
      }                                                        
      that.updating = new Date();                              
      if (/post/i.test(postMethod)) {
        var uri=urlCall+'?'+that.updating.getTime();
        that.AJAX.open("POST", uri, true);
        that.AJAX.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
        that.AJAX.send(passData);
      } else {
        var uri=urlCall+'?'+passData+'&timestamp='+(that.updating.getTime()); 
        that.AJAX.open("GET", uri, true);                             
        that.AJAX.send(null);                                         
      }              
      return true;                                             
    }                                                                           
  }
  var urlCall = url;        
  this.callback = callbackFunction || function () { };
}