This is an example for my AJAX blog post

AJAX_Example.js

(function(window,undef){

//get a new XMLHttpRequest object
function getXHR(){
    //for IE:
    if (window.ActiveXObject){
        try{ //newer version
            return new ActiveXObject('MSXML2.XMLHTTP');
       
        }catch (e){//older version
            return  new ActiveXObject('Microsoft.XMLHTTP');
        }
    }
   
   //for all other browsers
    return new XMLHttpRequest();
}


window['AJAX'] = function(url,method,async){
    //setting default values
    
    method = method || "get";
    async = (async === undef) ? true : async;
    
    var complete_funcs = [] //a stack of functions to call when request is done
        , headers = {"X-Requested-With":'XMLHttpRequest'} //a list of headers to send with the request
        , xhr = this.xhr = getXHR(); //the request object
    
    this.setHeader = function setHeader(key,value){
        headers[key] = value;
    }
    
    //add function to the complete event
    //accepts a N length list of functions
    this.onComplete = function onComplete(func){
            
            for (var i = 0; i<arguments.length; i++){
            //fo through all arguments passed to the function and add them to
            //the function stack
                complete_funcs.push(arguments[i]);
            }
    }
    
    //send the request with request data - a literal object of keys and values
    this.go = function go(data){
        var query = ""
             , sep = "";
        
        //go through all keys in data
        for (var key in data){
            
            if (data.hasOwnProperty(key)){
            //if the key isn't derived for the prototype, add it to the reuqest query:
            
                query += sep + encodeURIComponent(key) +"="+ encodeURIComponent(data[key]);
                sep = "&";
            }
        }
        
        
        
        if (method =='get'){
            this.xhr.open("GET",url+"?"+query,async);
            
            for (var key in headers){//add user headers
                if (headers.hasOwnProperty(key)) xhr.setRequestHeader(key,headers[key]);
            }
            
            this.xhr.send();
        
        }else{
            this.xhr.open("POST",url,async);
            
            for (var key in headers){//add user headers
                if (headers.hasOwnProperty(key)) xhr.setRequestHeader(key,headers[key]);
            }
            
            this.xhr.setRequestHeader("Content-type","application/x-www-form-urlencoded");
            this.xhr.send(query);
        }
    }    
    
    
        
    this.xhr.onreadystatechange = function(){
    //add the event handler
        if (xhr.readyState == 4){//if the request is done
                
                if  (xhr.status == 200) {//and the request is valid
                
                    for (var i = complete_funcs.length-1; i>=0; i--){
                    //call all functions in complete stack
                        complete_funcs[i](xhr.responseText,xhr);
                    } 
                }        
        }
    }
}

})(this);