https://lesiabart.pl/skin/pics/js/unveil.js

1/**
2 * jQuery Unveil
3 * A very lightweight jQuery plugin to lazy load images
4 * http://luis-almeida.github.com/unveil
5 *
6 * Licensed under the MIT license.
7 * Copyright 2013 Luís Almeida
8 * https://github.com/luis-almeida
9 */
10
11
12(function($) {
13
14	$.fn.unveil = function(threshold, callback, elem) {
15		
16		var $w = elem ? $(elem) : $(window);
17		var th = threshold || 0;
18		var retina = window.devicePixelRatio > 1;
19		var attrib = retina ? "data-src-retina" : "data-src";
20		var images = this;
21		var loaded;
22
23		this.one("unveil", function() {
24			var source = this.getAttribute(attrib);
25			source = source || this.getAttribute("data-src");
26			if (source) {
27				this.setAttribute("src", source);
28				if ( typeof callback === "function")
29					callback.call(this);
30			}
31		});
32
33		function unveil() {			
34			var woffset = ($w.offset() ? $w.offset().top : 0) - $(document).scrollTop();
35			var inview = images.filter(function() {
36				var $e = $(this);
37				if ($e.data('pauseUnveil')) return;
38				if ($e.css('display') == 'none') {//is(":hidden"))
39					return;
40				}
41
42				var wt = woffset + $w.scrollTop(); 
43				var wb = wt + $w.height();
44				var et = $e.offset().top - $(document).scrollTop();
45				var eb = et + $e.height();
46
47				return /*eb >= wt - th && */et <= wb + th;
48			});
49
50			loaded = inview.trigger("unveil");
51			images = images.not(loaded);
52		}
53
54
55		$w.on("scroll.unveil resize.unveil lookup.unveil", unveil);
56
57		unveil();
58
59		return this;
60
61	};
62
63})(window.jQuery || window.Zepto); 
64