Load Script

gistfile1.js

var loadScript = function(url, callback){
     var d = document,
          script = d.createElement('script');
     script.type = 'text/javascript';
     if(script.readyState){
          script.onreadystatechange = function(){
               if(script.readyState == 'loaded' ||     script.readyState == 'complete'){
                    script.onreadystatechange = null;
                    callback.call(this);
               }
          };
     }else{
          script.onload = function(){
               callback.call(this);
          };
     }
     script.src = url;
     d.getElementsByTagName('head')[0].appendChild(script);
};