smart-preloader.js

$.fn.dt_smartPreloader = function (action) {
  var args = arguments;
  return this.each(function (index, self) {
    var $self = $(self);
    var visibility = $self.css('visibility');

    /* wrap $self with a preloader div */
    $self.wrap($('<div>').addClass('preloader-mask ajaxLoading'));
    var $preloader = $self.parent();

    var actions = {
      start: function () {
        /* hide the loading element */
        $self.css('visibility', 'hidden');
      },
      stop: function () {
        /* restore initial visibility */
        $self.css('visibility', visibility);
        /* unwrap the element */
        $preloader.replaceWith($self);
      },
      load: function (url, callback) {
        actions.start();
        $preloader.load(url, function (data) {
          actions.stop();
          if (callback) callback($preloader.children());
        });
      }
    };
    actions[action].apply(this, Array.prototype.slice.call(args, 1));
  });
};