第三节 轮播

css样式

*{margin:0;padding:0}
.content{
    cursor: pointer;
    position: relative;
    width:600px;height:400px;
    margin-left: auto;margin-right: auto;
    border:1px solid #333;
}
#list{
    position: absolute;
    width:600px;
    height:400px;
}
#list img,#prev,#next,#btns{
    position: absolute;
}
#list img:not(:first-child){
    display: none;
}
#prev,#next{
    cursor: pointer;
    top:50%;transform: translateY(-50%);
    z-index: 100;width:40px;height:70px;
    background:url("../images/icon-slides.png");
    border:none;
}
#prev{
    background-position-x:-86px
}
#prev:hover{
    background-position: 0;
}
#next:hover{background-position-x: -43px}
#next{
    right:0;
    background-position-x:-125px;
}
#btns{z-index: 101;
    transform: translateX(-50%);
    bottom: 20px;left:50%;}
#btns .current{
    background:orangered;
}    
#btns>span{
    cursor: pointer;
    width:20px;
    height:20px;
    display: inline-block;
    border-radius: 50%;
    border:1px solid #fff;
    background-color:rgba(44,44,44,.3);
}

 <div class="content">
        <div id="list">
            <img src="images/01.png" alt="">
            <img src="images/02.png" alt="">
            <img src="images/03.png" alt="">
            <img src="images/04.png" alt="">
            <img src="images/05.png" alt="">
        </div>
        <button id="prev"></button>
        <button id="next"></button>
        <div id="btns">
            <span class="current"></span>
            <span></span>
            <span></span>
            <span></span>
            <span></span>
        </div>
    </div>

 <script>
        var prev=document.getElementById("prev");
        var next=document.getElementById("next");
        var lists=document.querySelectorAll("#list>img");
        var icons=document.querySelectorAll("#btns>span")
        var index=0;  //index  记录下标
        next.onclick=function(){
            index++;
            if(index>4){
                index=0;
            }
            console.log(index)
            for(let i=0;i<lists.length;i++){        //遍历图片
                lists[i].style.display="none"       //让所有图片都隐藏
            }
            lists[index].style.display="block"     //只让当前下标下的图片显示
            for(let i=0;i<icons.length;i++){       //遍历焦点
                icons[i].classList.remove("current")   //移去所有焦点
            }
            lists[index].classList.add("current")      //只让当前下标下的焦点增加
        }
        prev.onclick=function(){
            index--;
            if(index<0){
                index=4;
            }
            for(let i=0;i<lists.length;i++){
                lists[i].style.display="none";
            }
            lists[index].style.display="block"
            for(let i=0;i<icons.length;i++){       
                icons[i].classList.remove("current")   
            }
            lists[index].classList.add("current")   
        }
        /* 下标重置 */
        for(let i=0;i<icons.length;i++){   //遍历焦点
            icons[i].index=i;
            icons[i].onclick=function(){    //给焦点一个点击事件
                let currentIndex=this.index;     //指向当前index
                for(let i=0;i<lists.length;i++){
                    lists[i].style.display="none";
                }
                lists[currentIndex].style.display="block"
                for(let i=0;i<icons.length;i++){
                    icons[i].classList.remove("current")
                }
                icons[currentIndex].classList.add("current")
            }
        }
    </script>