code: function updatePointer(type, pointerEvent) {
      if(type == EVENT_END) {
        delete this.pointers[pointerEvent.pointerId];
      }
      else {
        pointerEvent.identifier = pointerEvent.pointerId;
        this.pointers[pointerEvent.pointerId] = pointerEvent;
      }
  
      // it's save to use Object.keys, since pointerEvents are only in newer browsers
      return Object.keys(this.pointers).length;
    }
docs: update the position of a pointer
  @param   {String}   type             EVENT_END
  @param   {Object}   pointerEvent