/** constructor 
   
       @param duration integer seconds
       @param <optional> function to run while waiting.
       
    */
   function Pause(duration, busy){
      this.duration= duration * 1000;
      this.busywork = null; // function to call while waiting.
      this.runner = 0;

      if (arguments.length == 2) {
         this.busywork = busy;
      }

      this.pause(this.duration);

   } // Pause class

   /** pause method 
   
       @param duration: integer in seconds
       
    */
   Pause.prototype.pause = function(duration){
      if ( (duration == null) || (duration < 0)) {return;}

      var later = (new Date()).getTime() + duration;

      while(true){
         if ((new Date()).getTime() > later) {
            break;
         }

         this.runner++;

         if (this.busywork != null) {
            this.busywork(this.runner);
         }

      } // while

   } // pause method