JavaScript实现轮播图效果完整代码示例

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }
        ul {
            list-style: none;
        }
        #box {
            margin: 30px auto;
            width: 590px;
            height: 340px;
            position: relative;
        }
 
        #banner-list > li {
            position: absolute;
            left: 0;
            right: 0;
            opacity: 0;
            /*过渡动画*/
            transition: opacity 2s ease;
        }
 
        #left, #right {
            width: 30px;
            height: 60px;
            text-align: center;
            line-height: 60px;
            font-size: 24px;
            color: rgba(255,255,255,0.7);
            background-color: rgba(0,0,0,0.3);
            position: absolute;
            top: 50%;
            margin-top: -30px;
            z-index: 3;
        }
 
        #right {
            right: 0;
        }
 
        #tag-list {
            width: 130px;
            position: absolute;
            left: 50%;
            bottom: 8px;
            margin-left: -55px;
        }
 
        #tag-list > li {
            float: left;
            width: 18px;
            height: 18px;
            margin: 4px;
            text-align: center;
            line-height: 18px;
            font-size: 13px;
            background-color: white;
            border-radius: 9px;
            /*过渡动画*/
            transition: background-color 1s ease;
        }
    </style>
    <script>
        window.onload = function (){
            //获取tag_list和圆圈list
            var tag_list = document.getElementById("tag-list");
            var list = tag_list.children;
 
            //1.获取 ul(banner_list) 和 所有的li
            let banner_list = document.getElementById("banner-list");
            let bannerLi = banner_list.children;
 
            //2.默认显示第一张banner
            bannerLi[0].className = "current-banner"
            bannerLi[0].style.opacity = 1
            list[0].style.backgroundColor = "red"
 
            //3.索引从0开始，默认显示第一张。
            //count表示当前显示页面的索引
            let count = 0;
 
            //4.点击>向右切换
            var right = document.getElementById("right");
            right.onclick = function (){
                //4.1先将当前页面隐藏
                bannerLi[count].className = ""
                bannerLi[count].style.opacity = 0
                list[count].style.backgroundColor = "white"
 
                //4.2.页码加1,当到第6张(index=5)，切换到第一张(index=0)
                if (++count == 5){
                    count = 0
                }
 
                //4.3 设置当前页码为显示
                bannerLi[count].className = "current-banner"
                bannerLi[count].style.opacity = 1
                list[count].style.backgroundColor = "red"
            }
 
            //和right差不多，修改下条件
            var left = document.getElementById("left");
            left.onclick = function (){
                //4.1先将当前页面隐藏
                bannerLi[count].className = ""
                bannerLi[count].style.opacity = 0
                list[count].style.backgroundColor = "white"
 
                //4.2.页码减1,当到第0张(index=-1)，切换到第5张(index=4)
                if (--count == -1){
                    count = 4
                }
 
                //4.3 设置当前页码为显示
                bannerLi[count].className = "current-banner"
                bannerLi[count].style.opacity = 1
                list[count].style.backgroundColor = "red"
            }
 
            //给所有圆圈绑定鼠标事件
            for (let i = 0; i < list.length; i++) {
                list[i].onmouseenter= function (){
                    //设置圆圈样式
                    list[count].style.backgroundColor = "white"
                    list[i].style.backgroundColor = "red"
                    //设置banner图样式
                    bannerLi[count].className = ""
                    bannerLi[count].style.opacity = 0
                    bannerLi[i].className = "current-banner"
                    bannerLi[i].style.opacity = 1
                    //将count置为i
                    count = i
                }
            }
        }
    </script>
</head>
<body>
    <div id="box">
        <ul id="banner-list">
            <li class="current-banner"><img src="banner-img/11.jpg" alt=""></li>
            <li><img src="banner-img/22.jpg" alt=""></li>
            <li><img src="banner-img/33.jpg" alt=""></li>
            <li><img src="banner-img/44.jpg" alt=""></li>
            <li><img src="banner-img/55.jpg" alt=""></li>
        </ul>
        <span id="left">&lt;</span>
        <span id="right">&gt;</span>
        <div>
            <ul id="tag-list">
                <li>1</li>
                <li>2</li>
                <li>3</li>
                <li>4</li>
                <li>5</li>
            </ul>
        </div>
    </div>
</body>
</html>