最简单的原生js轮播图（适合新手）-蒲公英云

<!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>
<script src="jquery.js"></script>
<style>
*{
    margin: 0px;
    padding:0px;
    list-style: none;
    text-decoration: none;
}
#flash{ /*根据图片的大小来设置外层div的大小*/
    width: 520px;
    height: 280px;
    margin: 0 auto;
    position: relative; /*设置div定位，方便之后图片及圆点位置的设定*/
    border:1px solid black;
}
#flash img{
    width: 100%;
    height: 100%;
    position: absolute; /*设置所有图片重叠*/
    left: 0px;
    top: 0px;
    display: none; /*设置所有图片隐藏，通过改变第一个图片的行间样式来使第一个图片显示*/
}
#flash ul{
    width: 150px;
    height: 25px;
    border-radius: 20px;
    background-color:rgba(255,255,255,0.5);
    position: absolute;
    left: 35%;
    bottom: 10%;
}
#flash ul li{
    width: 12px;
    height: 12px;
    margin-top:5px;
    background-color: #fff;
    border-radius: 50%;
    margin-left: 15px;
    float: left;
}
#flash ul .li_1{
    background-color: #f40; /*设置第一个圆点背景色为红色*/
}
#flash .span-r{
    width: 50px;
    height: 50px;
    border-radius: 50%;
    position: absolute;
    right: 2%;
    top: 45%;
    background-color: rgba(255,255,255,0.5);
}
#flash .span-r span{
    width: 100%;
    height:100%;
    color:rgba(0,0,0,0.5);
    font-size: xx-large;
    font-weight: 700;
    line-height: 50px;
    margin-left: 15px;
    cursor: pointer;
}
#flash .span-l{
    width: 50px;
    height: 50px;
    border-radius: 50%;
    position: absolute;
    left: 2%;
    top: 45%;
    background-color: rgba(255,255,255,0.5);
}
#flash .span-l span{
    width: 100%;
    height:100%;
    color:rgba(0,0,0,0.5);
    font-size: xx-large;
    font-weight: 700;
    line-height: 50px;
    margin-left: 15px;
    cursor: pointer;
}
</style>
</head>
<div id="flash">
<img src="img1.jpg" alt="" style="display: block">
<img src="img2.jpg" alt="">
<img src="img3.jpg" alt="">
<img src="img4.jpg" alt="">
<img src="img5.jpg" alt="">
<ul>
<li class="li_1"></li>
<li></li>
<li></li>
<li></li>
<li></li>
</ul>
<div class="span-r">
<span>></span>
</div>
<div class="span-l">
<span><</span>
</div>
</div>
<body>
<script>
    var div = document.getElementById('flash');
    var img = div.getElementsByTagName('img'); /*选中div下所有的图片*/
    var ul = document.getElementsByTagName('ul')[0];
    var li = ul.getElementsByTagName('li');
    var div_r = document.getElementsByTagName('div')[1];
    // var span_r = div_r.getElementsByTagName('span');
    var div_l = document.getElementsByTagName('div')[2];
    // var sapn_l = div_l.getElementsByTagName('span');
    var len = img.length;
    var count = 0; /*设置count来显示当前图片的序号*/
function run(){ /*将定时器里的函数提取到外部*/
    count++;
    count = count==5?0:count; /*当图片加载到最后一张时，使其归零*/
    for(var i=0;i<len;i++){    
        img[i].style.display = 'none'; /*利用for循环使除当前count位其他图片隐藏*/
    }
    img[count].style.display = 'block'; /*显示当前count的值所代表的图片*/
    for(var i=0;i<li.length;i++){
        li[i].style.backgroundColor = "#fff"; /*原理同上*/
    }
    li[count].style.backgroundColor = "#f40";
}
    var timer = setInterval(run,1000); /*定义定时器，使图片每隔1s更换一次*/
    div.onmouseover = function(){
    clearInterval(timer);
}
    div.onmouseleave = function(){ /*定义鼠标移出事件，当鼠标移出div区域，轮播继续*/
    timer = setInterval(run,1000);
}
    for(var i=0;i<len;i++){
        li[i].index = i; /*定义index记录当前鼠标在li的位置*/
        li[i].onmouseenter = function(){ /*定义鼠标经过事件*/
        for(var i=0;i<len;i++){ /*通过for循环将所有图片隐藏，圆点背景设为白色*/
            li[i].style.background = '#fff';
            img[i].style.display = 'none';
        }
    this.style.background = '#f40'; /*设置当前所指圆点的背景色*/
    img[this.index].style.display = 'block'; /*使圆点对应的图片显示*/
    }
}
    div_r.onclick = function(){ /*因为span没有设置宽高，直接把事件添加到他的父级*/
    run(); /*直接调用现成的run函数*/
}
function reverse(){
    count--;
    count = count==-1?4:count;
    for(var i=0;i<len;i++){
        img[i].style.display = 'none'; /*利用for循环使除当前count位其他图片隐藏*/
    }
    img[count].style.display = 'block'; /*显示当前count的值所代表的图片*/
    for(var i=0;i<li.length;i++){
        li[i].style.backgroundColor = "#fff"; /*原理同上*/
    }
    li[count].style.backgroundColor = "#f40";
}
    div_l.onclick = function(){
    reverse(); /*重新设置函数*/
}
</script>
</body>
</html>
var div = document.getElementById('flash');
    var img = div.getElementsByTagName('img'); /*选中div下所有的图片*/
    var ul = document.getElementsByTagName('ul')[0];
    var li = ul.getElementsByTagName('li');
    var div_r = document.getElementsByTagName('div')[1];
    // var span_r = div_r.getElementsByTagName('span');
    var div_l = document.getElementsByTagName('div')[2];
    // var sapn_l = div_l.getElementsByTagName('span');
    var len = img.length;
    var count = 0; /*设置count来显示当前图片的序号*/
function run(){ /*将定时器里的函数提取到外部*/
    count++;
    count = count==5?0:count; /*当图片加载到最后一张时，使其归零*/
    for(var i=0;i<len;i++){
        img[i].style.display = 'none'; /*利用for循环使除当前count位其他图片隐藏*/
    }
    img[count].style.display = 'block'; /*显示当前count的值所代表的图片*/
    for(var i=0;i<li.length;i++){
    li[i].style.backgroundColor = "#fff"; /*原理同上*/
    }
    li[count].style.backgroundColor = "#f40";
    }
    var timer = setInterval(run,1000); /*定义定时器，使图片每隔1s更换一次*/
    div.onmouseover = function(){
    clearInterval(timer);
    }
    div.onmouseleave = function(){ /*定义鼠标移出事件，当鼠标移出div区域，轮播继续*/
    timer = setInterval(run,1000);
    }
    for(var i=0;i<len;i++){
        li[i].index = i; /*定义index记录当前鼠标在li的位置*/
        li[i].onmouseenter = function(){ /*定义鼠标经过事件*/
    for(var i=0;i<len;i++){ /*通过for循环将所有图片隐藏，圆点背景设为白色*/
        li[i].style.background = '#fff';
        img[i].style.display = 'none';
    }
    this.style.background = '#f40'; /*设置当前所指圆点的背景色*/
    img[this.index].style.display = 'block'; /*使圆点对应的图片显示*/
        }
    }
    div_r.onclick = function(){ /*因为span没有设置宽高，直接把事件添加到他的父级*/
    run(); /*直接调用现成的run函数*/
}
function reverse(){
    count--;
    count = count==-1?4:count;
    for(var i=0;i<len;i++){
        img[i].style.display = 'none'; /*利用for循环使除当前count位其他图片隐藏*/
    }
    img[count].style.display = 'block'; /*显示当前count的值所代表的图片*/
    for(var i=0;i<li.length;i++){
        li[i].style.backgroundColor = "#fff"; /*原理同上*/
    }
    li[count].style.backgroundColor = "#f40";
}
    div_l.onclick = function(){
    reverse(); /*重新设置函数*/
}