一定時間ごとに画像を切り替えたい。

jsで一定時間ごとにクラスを付け替えて、画像を切り替えていきたいです。

https://www.elan-v.com/
上記サイト、トップの画像切り替えのようにしたくて
使われていそうなコードを切り取ってみたのですが、
うまくいきません。

発生している問題・エラーメッセージ

liにcurrentクラスがつかないです。

該当のソースコード

html
1!DOCTYPE html>
2<html lang="ja">
3<head>
4  <meta charset="UTF-8">
5  <meta name="viewport" content="width=device-width, initial-scale=1.0">
6  <link rel="stylesheet" href="css/style.css">
7</head>
8<body id="page-home">
9  <section class="sec-mv" id="sec-mv">
10    <ul class="list-mv" id="js-list-mv">
11      <li></li>
12      <li></li>
13      <li></li>
14      <li></li>
15    </ul>
16  </section>
17  <script src="https://code.jquery.com/jquery-2.2.4.min.js"></script>
18  <script type="text/javascript" src="script/script.js"></script>
19</body>
20</html>

css
1@keyframes slide-left {
2	0% {
3		transform:translateX(0);
4	}
5	100% {
6		transform:translateX(-40px);
7	}
8}
9@keyframes slide-right {
10	0% {
11		transform:translateX(-40px);
12	}
13	100% {
14		transform:translateX(0);
15	}
16}
17
18.sec-mv {
19  position: relative;
20  width: 100%;
21  height: 100vh;
22}
23.list-mv li {
24  opacity: 0;
25  visibility: hidden;
26  position: absolute;
27  top: 0;
28  left: 0;
29  right: -40px;
30  bottom: 0;
31  overflow: hidden;
32  margin: auto;
33}
34.list-mv li.current {
35  transition: all .5s cubic-bezier(0.39, 0.575, 0.565, 1);
36  opacity: 1;
37  visibility: visible;
38  z-index: 0;
39  transform: rotate(0.0001deg);
40  outline: 1px solid transparent;
41  backface-visibility: hidden;
42}
43
44.list-mv li:nth-of-type(1).current,
45.list-mv li:nth-of-type(3).current {
46  animation: slide-left 5s linear forwards;
47}
48.list-mv li:nth-of-type(2).current,
49.list-mv li:nth-of-type(4).current {
50  animation: slide-right 5s linear forwards;
51}
52
53.list-mv li:nth-of-type(1) {
54	background: url("../image/adam-winger-3nBzt3Jdeh4-unsplash.jpg") center center no-repeat;
55	background-size: cover;
56}
57.list-mv li:nth-of-type(2) {
58	background: url("../image/ashkan-forouzani-wRufXGaO8ok-unsplash.jpg") center center no-repeat;
59	background-size: cover;
60}
61.list-mv li:nth-of-type(3) {
62	background: url("../image/guus-baggermans-cg599DTeS8w-unsplash.jpg") center center no-repeat;
63	background-size: cover;
64}
65.list-mv li:nth-of-type(4) {
66	background: url("../image/henry-co-GkuZdv11Gfo-unsplash.jpg") center center no-repeat;
67	background-size: cover;
68}
69

js
1$(function() {
2	var $body = $('body');
3	var $win = $(window);
4	var $winHeight = Math.floor($win.height());
5	var $winWidth = Math.floor($win.width());
6
7	$.fn.slidemv = function() {
8		var $mv = this;
9		var $list_mv = $('#js-list-mv');
10		var current = 0;
11		var length = $list_mv.find('li').length;
12		var timerId = null;
13		var first_flg = true;
14		var delay = 5000;
15		var touchmove_flg = false;
16	
17		function autoChangeDevice() {
18			current++;
19			if (current >= length) {
20				current = 0;
21			}
22			
23			setDevice();
24		}
25		
26		function setDevice() {
27			clearInterval(timerId);
28			timerId = null;
29			$list_mv.find('li').removeClass('current').eq(current).addClass('current');
30			timerId = setInterval(autoChangeDevice, delay);
31		}
32
33		function screenTest() {
34			clearInterval(timerId);
35			timerId = setInterval(autoChangeDevice, delay);
36			setDevice();
37		}
38		screenTest();
39	}
40
41	$win.on('resize load', function() {
42		$winHeight = Math.floor($win.height());
43		$winWidth = Math.floor($win.width());
44	})
45
46	if (ua.Mobile) {
47		$.fn.fullmv = function() {
48			var $mv = $(this);
49			function resizeMv() {
50				$mv.css({
51					width: $winWidth,
52					height: $winHeight
53				});
54			}
55			$win.on('resize', resizeMv);
56			resizeMv();
57		}
58		$win.on('load', function() {
59			$('#sec-mv').fullmv();
60		});
61  }
62});