https://www.revolutionchiropractor.com/plugins/editor/cms/componen…/assets/js/lazy-load-sections.js?v.1.257

1+function ($) {
2	"use strict";
3
4	$(function () {
5		/**  @type {{forEach: function(function(Element, number?, any?):void):void}} */
6		var lazyloadBgImages = document.querySelectorAll('.section-lazy');
7		if (!('forEach' in lazyloadBgImages)) {
8			// Have to convert nodeList to array because not all supported browsers have a 'forEach' on NodeLists
9			lazyloadBgImages = $.makeArray(lazyloadBgImages);
10		}
11		/** @type {function (Element, number?): void} */
12		var nodeAction;
13
14		/**
15		 * @param {Element} section
16		 */
17		function removeClass(section) {
18			section.classList.remove('section-lazy');
19		}
20
21		if ('IntersectionObserver' in window) {
22			nodeAction = (function () {
23				var imageObserver = new IntersectionObserver(watcher, {rootMargin: '0px 0px 134% 0px'});
24				function watcher(entries, observer) {
25					entries.forEach(function (entry) {
26						if (entry.isIntersecting || entry.intersectionRatio !== 0) {
27							var section = entry.target;
28							removeClass(section);
29							observer.unobserve(section);
30						}
31					});
32				}
33
34				return function (image) {
35					imageObserver.observe(image);
36				};
37			})();
38		} else {
39			nodeAction = (function () {
40				var count = 0, autoLoadDistance = window.innerHeight * 2;
41				/** @type {function (Element?): boolean} */
42				var isInView = function (el) {
43					var inView = autoLoadDistance >= el.getBoundingClientRect().top;
44					// Reduce Repaint calculations if out of view by caching result, since we are traversing linearly
45					if (!inView) isInView = alwaysFalse;
46					return inView;
47				};
48				function alwaysFalse() { return false; }
49
50				return function (el) {
51					if (isInView(el)) {
52						removeClass(el);
53					} else {
54						setTimeout(function () {removeClass(el);}, (count += 1) * 300);
55					}
56				};
57			})();
58		}
59
60		lazyloadBgImages.forEach(nodeAction);
61	})
62}(window.jQuery);