JavaScript AJAX lazy loading function_javascript skills

/**
* JS lazy function
​*/
 
function ajax(){
    if(typeof XMLHttpRequest != "undefined"){
        ajax = function(){
            return new XMLHttpRequest();   
        };
    }else if(typeof ActiveXObject != "undefined"){
        ajax = function(){
            if(typeof arguments.callee.activeXString != "string"){
                var versions = ["MSXML2.XMLHttp.6.0","MSXML2.XMLHttp.3.0","MSXML2.XMLHttp"];   
 
                for(var i=0,k=version.length;i                     try{
                        var xhr = new ActiveXObject(versions[i]);  
                        arguments.callee.activeXString = versions[i];
                        return xhr;
                    }catch(ex){
                        throw ex;  
                    }
                }
            }  
 
            return new ActiveXObject(arguments.callee.activeXString);
        }
    }else{
        ajax = function(){
            throw "No XHR object"; 
        }
    }
 
    return ajax();
}