function Script(callback){
        var js = document.createElement("script");
        this.js = js;
        js.setAttribute("type",'text/javascript');
        var head = document.getElementsByTagName('head')[0];
        head.appendChild(js);        if(navigator.appName.toLowerCase().indexOf('netscape') == -1){
            js.onreadystatechange = function(){                if(js.readyState == 'complete'){
                    callback(js);
                }
            }
        }else{
            js.onload = function(){
                callback(js);
            }
        }
    }    Script.prototype.get = function(url){
        this.js.src = url;
    }    function script_onload(script){
        alert(script.src);
    }
    var load_js = new Script(script_onload);
    load_js.get('http://static.gongju.com/js/jquery-1.4.4.min.js');