老师，呼吸轮播图做出了没有效果，帮我看下

来源：4-12 编程练习

慕的地5368065

2021-05-27 11:14:11

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        .carousel {
            width: 650px;
            height: 360px;
            border: 1px solid #000;
            margin: 50px auto;
            position: relative;

        }

        .carousel ul {
            list-style: none;


        }

        .carousel ul li {
            top: 0;
            left: 0;
            position: absolute;
            /* 图片透明度为0 */
            opacity: 0;
            transition: opacity .5s ease 0s;

        }
        /* 只有第一张透明度为1 */
        .carousel ul li:first-child{
            opacity: 1;
        }

        .carousel .leftbtn {
            left: 20px;
            width: 50px;
            height: 50px;
            top: 50%;
            margin-top: -25px;
            background-color: rgba(0, 38, 255, 0.493);
            position: absolute;
            border-radius: 50%;
        }

        .carousel .rightbtn {
            right: 20px;
            width: 50px;
            height: 50px;
            top: 50%;
            margin-top: -25px;
            background-color: rgba(0, 38, 255, 0.493);
            position: absolute;
            border-radius: 50%;
        }
    </style>
</head>

<body>
    <div class="carousel">
        <ul id="list">
            <li><img src="/images/beijing/0.jpg" alt=""></li>
            <li><img src="/images/beijing/1.jpg" alt=""></li>
            <li><img src="/images/beijing/2.jpg" alt=""></li>
            <li><img src="/images/beijing/3.jpg" alt=""></li>
            <li><img src="/images/beijing/4.jpg" alt=""></li>
        </ul>
        <a href="javascript:;" class="leftbtn" id="leftbtn"></a>
        <a href="javascript:;" class="rightbtn" id="rightbtn"></a>
    </div>
    <script>
        // 得到按钮和ul,ul整体进行运动
        var leftbtn = document.getElementById('leftbtn');
        var rightbtn = document.getElementById('rightbtn');
        var list = document.getElementById('list');
        var lis=list.getElementsByName('li');
        // 当前是第几张图显示
        var idx=0;
        // 函数节流
        var lock=true;
        // 右按钮监听
        rightbtn.onclick=function(){
            // 判断锁的状态
            if(!lock)return;
            lock=false;
            // 老图淡出
            lis[idx].style.opacity=0;
            idx++;
            if(idx>4) idx=0;
            lis[idx].style.opacity=1;
            // 动画结束之后开锁
            setTimeout(function(){
                lock=true;
            },1000);
        }
         // 左按钮监听
         leftbtn.onclick=function(){
            // 判断锁的状态
            if(!lock)return;
            lock=false;
            // 老图淡出
            lis[idx].style.opacity=0;
            idx--;
            if(idx<0) idx=4;
            lis[idx].style.opacity=1;
            // 动画结束之后开锁
            setTimeout(function(){
                lock=true;
            },1000);
        }

    </script>
</body>

</html>