需求：让幻灯片切换时有动画过渡效果
每个li都绝对定位到一个位置，通过opacity和z-index层级操作其显示，通过transition:1s linear;生成动画过渡效果
.picList li {
position: absolute;
left: 0;
top: 0;
opacity: 0;
transition: 1s linear;
z-index: 1;
}<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
.wrap {
position: relative;
margin: 30px auto;
width: 640px;
}
.picList {
margin: 0;
padding: 0;
list-style: none;
width: 640px;
height: 368px;
}
.picList li {
position: absolute;
left: 0;
top: 0;
opacity: 0;
transition: 1s linear;
z-index: 1;
}
.picList .show {
opacity: 1;
z-index: 2;
}
.nav {
display: flex;
justify-content: center;
align-items: center;
height: 20px;
}
.nav a {
position: relative;
z-index: 4;
width: 12px;
height: 12px;
margin: 0 5px;
background: #000;
border-radius: 6px;
}
.nav span {
display: none;
position: absolute;
left: -27px;
top: -50px;
}
.nav a:hover span {
display: block;
}
.nav img {
display: block;
width: 64px;
height: 36.8px;
border: 1px solid #000;
}
.nav span:after {
content: "";
position: absolute;
left: 25px;
bottom: -16px;
width: 0;
height: 0;
border: 8px solid #000;
border-color: #000 transparent transparent;
}
.nav .active {
background: #f60;
}
.btn {
position: absolute;
top: 120px;
width: 40px;
height: 40px;
background: #fff;
color: #000;
font: 14px/40px "宋体";
text-align: center;
text-decoration: none;
z-index: 3;
}
.prev {
left: 0;
}
.next {
right: 0;
}
</style>
</head>
<body>
<div class="wrap">
<ul class="picList">
<li class="show">
<a href="#1">
<img src="img/img1.jpg" />
</a>
</li>
<li>
<a href="#2">
<img src="img/img2.jpg" />
</a>
</li>
<li>
<a href="#3">
<img src="img/img3.jpg" />
</a>
</li>
<li>
<a href="#4">
<img src="img/img4.jpg" />
</a>
</li>
</ul>
<nav class="nav">
<a href="javascript:;" class="active">
<span><img src="img/img1.jpg" /></span>
</a>
<a href="javascript:;">
<span><img src="img/img2.jpg" /></span>
</a>
<a href="javascript:;">
<span><img src="img/img3.jpg" /></span>
</a>
<a href="javascript:;">
<span><img src="img/img4.jpg" /></span>
</a>
</nav>
<!-- <a href="javascript:;" class="btn prev">prev</a>
<a href="javascript:;" class="btn next">next</a> -->
</div>
<script>
var wrap = document.querySelector(".wrap");
var lis = wrap.querySelectorAll(".picList li");
var nav = wrap.querySelectorAll(".nav a");
nav.forEach(function(a,index){
a.onclick = function(){
nav.forEach(function(a,index){
lis[index].classList.remove("show");
a.classList.remove("active");
});
lis[index].classList.add("show");
a.classList.add("active");
};
});
</script>
</body>
</html>
