js原生轮播图

1.先画轮播图片样式

2.再画轮播按钮

3.样式完成，写js代码

4.获取所有节点

<!DOCTYPE html>
<html>
<head>
<title>轮播图</title>

<style type="text/css">
.wrap{
width: 800px;
height: 400px;
position: relative;
}
.list{
width: 800px;
height: 400px;
list-style: none;
position: relative;
padding-left: 0px;
}
.item{
position: absolute;
width: 100%;
height: 100%;
color: white;
font-size:20px;
opacity: 0;
transition: all .8s;
z-index: 2
}
/*nth-child()用于选择子元素,参数是从0开始的*/
.item:nth-child(1){
background-color: black;
}
.item:nth-child(2){
background-color: red;
}
.item:nth-child(3){
background-color: green;
}
.item:nth-child(4){
background-color: yellow;
}
.item:nth-child(5){
background-color: pink;
}
.btn{
width: 50px;
height: 100px;
position: absolute;
top: 150px;
z-index: 100;
}
#goPre{
left: 0px;
}
#goNext{
right: 0px;
}
.item.active{
z-index: 10;
}
.pointList{
padding-left: 0px;
list-style: none;
position: absolute;
right: 20px;
bottom: 20px;
z-index: 1000;
}
.point{
width: 10px;
height: 10px;
background-color: rgba(0,0,0,0.4);
border-radius: 100%;
float: left;
margin-right: 14px;
border-style: solid;
border-width: 2px;
border-color: rgba(255,255,255,0.6);
cursor: pointer;
}
.point .active{
background-color: rgba(255,255,255,0.8);
}
</style>
</head>
<body>
<div class="wrap">
<ul class="list">
<li class="item active">0</li>
<li class="item">1</li>
<li class="item">2</li>
<li class="item">3</li>
<li class="item">4</li>
</ul>
<ul class="pointList">
<li class="point" data-index='0'></li>
<li class="point" data-index='1'></li>
<li class="point" data-index='2'></li>
<li class="point" data-index='3'></li>
<li class="point" data-index='4'></li>
</ul>
<button type="button" class="btn" id="goPre"><</button>
<button type="button" class="btn" id="goNext">></button>

</div>

</body>
<script type="text/javascript">

// 获取所有class为item的节点
var items = document.getElementsByClassName('item');
// 获取id为goPre的节点
var goPreBtn = document.getElementById('goPre');
// 获取id为goNext的节点
var goNextBtn = document.getElementById('goNext');

var points = document.getElementsByClassName('point');

var index = 0; //表示第几张图片在展示 --> 第几张图片有active这个类名
// 第几个点在展示

// 清除active
var clearActive = function(){
for(var i = 0;i < items.length;i++){
items[i].className = 'item';
}
for(var i = 0;i < points.length;i++){
points[i].className = 'point';
}
}

// 把想要的加上active,其余的都是item,把想要的留下，不想要的都删掉
var goIndex = function(){
clearActive();
items[index].className = 'item active';
points[index].className = 'point active';

}

var goNext = function(){

if(index < 4){
index ++;
}else{
index = 0
}
goIndex();
}

var goPre = function(){

if(index == 0){
index = 4;
}else{
index --;
}
goIndex();
}

goNextBtn.addEventListener('click',function(){
goNext();
});

goPreBtn.addEventListener('click',function(){
goPre();
});

for(let i= 0; i <points.length;i++){
points[i].addEventListener('click',function(){
var pointIndex = this.getAttribute('data-index');
index = pointIndex;
goIndex();
});
}
</script>
</html>

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