Bookmarklet based on loading scripts

bookmarklet.js

// Bookmarklet Example
// javascript:(function(){ })();

// load script For bookmarklet

var head = document.getElementsByTagName("head")[0];
var script = document.createElement("script");
script.type = "text/javascript";
script.src = "helper.js";
head.appendChild(script);

var loadScripts = function(array,callback){
     var array = array||["https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js",
          "http://documentcloud.github.com/underscore/underscore-min.js",
          "http://documentcloud.github.com/backbone/backbone-min.js"];
     var loader = function(src,handler){ 
          var script = document.createElement("script"); 
          script.src = src; 
          script.onload = script.onreadystatechange = function(){ 
               script.onreadystatechange = script.onload = null; 
               if(/MSIE ([6-9]+\.\d+);/.test(navigator.userAgent)){
                    window.setTimeout(function(){handler();},8,this); 
               } else {
                    handler(); 
               };
          } 
          var head = document.getElementsByTagName("head")[0]; 
          (head || document.body).appendChild( script ); 
     }; 
     (function(){ 
          if(array.length!=0){ 
               loader(array.shift(),arguments.callee); 
          }else{ 
               callback && callback(); 
          } 
     })(); 
};


var lib_tests = {"https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js":typeof jQuery != "undefined" && jQuery.ajax,
     "http://documentcloud.github.com/underscore/underscore-min.js":typeof _ != "undefined" && _.map,
     "http://documentcloud.github.com/backbone/backbone-min.js":typeof Backbone != "undefined" && Backbone.View};
for(var i in lib_tests){
     console.log(lib_tests[i]);
}