activity.js

var Activity = (function() {
  var count = 0;

  var show = $.fancybox.showActivity;
  var hide = $.fancybox.hideActivity;

  var start = function() {
    ++count;
    show();
  };

  var stop = function() {
    if (--count < 1) {
      count = 0;
      hide();
    }
  };

  return { start: start, stop: stop };
}());