function init_func(f_name) {
   if (document.getElementById(f_name)) { 
     return;
   }
   var head = document.getElementsByTagName("head")[0];
   script = document.createElement('script');
   script.id = f_name;
   script.type = 'text/javascript';
   script.src = "/js/"+f_name+".js";
   head.appendChild(script);
 }