https://www.bwcumc.org/_assets/js/lib/mk032Libraries/jquery.offscreen.js

1/*
2 * jQuery offscreen plugin
3 *
4 * Copyright Cory LaViska for A Beautiful Site, LLC
5 *
6 * @license: http://opensource.org/licenses/MIT
7 *
8 */
9(function($) {
10  $.extend($.expr[':'], {
11    'off-top': function(el) {
12      return $(el).offset().top < $(window).scrollTop();
13    },
14    'off-right': function(el) {
15      return $(el).offset().left + $(el).outerWidth() - $(window).scrollLeft() > $(window).width();
16    },
17    'off-bottom': function(el) {
18      return $(el).offset().top + $(el).outerHeight() - $(window).scrollTop() > $(window).height();
19    },
20    'off-left': function(el) {
21      return $(el).offset().left < $(window).scrollLeft();
22    },
23    'off-screen': function(el) {
24      return $(el).is(':off-top, :off-right, :off-bottom, :off-left');
25    }
26  });
27})(jQuery);