SOURCE

// 设置一个参数记录当前是第几张图片
var slideIndex = 1;
showSlides(slideIndex);


// 设置按钮的点击事件
function plusSlides(n) {
    showSlides(slideIndex += n);
}


// 设置最下边小原点的点击事件
function currentSlide(n) {
    showSlides(slideIndex = n);
}

// 设置当前在第几张的计算方式
function showSlides(n) {
    var i;
    var slides = document.getElementsByClassName("mySlides");
    var dots = document.getElementsByClassName("dot");
    if (n > slides.length) { slideIndex = 1 }
    if (n < 1) { slideIndex = slides.length }
    for (i = 0; i < slides.length; i++) {
        slides[i].style.display = "none";
    }
    for (i = 0; i < dots.length; i++) {
        dots[i].className = dots[i].className.replace(" active", "");
    }
    // 一旦设置这个属性，所在的图片就会显示
    slides[slideIndex - 1].style.display = "block";
    // 一旦设置这个属性，所在的小圆点就会变化
    dots[slideIndex - 1].className += " active";
}











// 定时轮播

// var slideIndex = 0;
// showSlides();
 
// function showSlides() {
//     var i;
//     var slides = document.getElementsByClassName("mySlides");
//     var dots = document.getElementsByClassName("dot");
//     for (i = 0; i < slides.length; i++) {
//        slides[i].style.display = "none";  
//     }
//     slideIndex++;
//     if (slideIndex > slides.length) {slideIndex = 1}    
//     for (i = 0; i < dots.length; i++) {
//         dots[i].className = dots[i].className.replace(" active", "");
//     }
//     slides[slideIndex-1].style.display = "block";  
//     dots[slideIndex-1].className += " active";
//     setTimeout(showSlides, 2000); // 切换时间为 2 秒

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

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0,,shrink-to-fit=no">
    <title>响应式轮播图</title>

    <!-- <link rel="stylesheet" href="1.css"> -->
</head>

<body>

    <!-- 设置图片组（三张图片） -->
    <div class="slideshow-container">
        <div class="mySlides fade">
            <div class="numbertext">1 / 3</div>
            <img src="img/1.jpg" style="width:100%">
            <div class="text">美丽的山川</div>
        </div>

        <div class="mySlides fade">
            <div class="numbertext">2 / 3</div>
            <img src="img/2.jpg" style="width:100%">
            <div class="text">绚丽的云彩</div>
        </div>

        <div class="mySlides fade">
            <div class="numbertext">3 / 3</div>
            <img src="img/3.jpg" style="width:100%">
            <div class="text">呆萌的兔子</div>
        </div>

        <!-- 设置按钮，并添加一个js事件 -->
        <a class="prev" onclick="plusSlides(-1)">❮</a>
        <a class="next" onclick="plusSlides(1)">❯</a>
    </div>
    <br>

    <!-- 设置底部原点，并添加一个js事件 -->
    <div style="text-align:center">
        <span class="dot" onclick="currentSlide(1)"></span>
        <span class="dot" onclick="currentSlide(2)"></span>
        <span class="dot" onclick="currentSlide(3)"></span>
    </div>

    <script src="1.js"></script>
</body>

</html>

* {
    /* 不清除盒子的margin，默认还有8px */
    box-sizing: border-box
}

body {
    font-family: Verdana, sans-serif;
}

.mySlides {
    /* 先让他们都隐藏起来 */
    display: none
}


/* 幻灯片容器 */

.slideshow-container {
    max-width: 1000px;
    position: relative;
    margin: auto;
}


/* 下一张 & 上一张 按钮 */

.prev,
.next {
    cursor: pointer;
    position: absolute;
    top: 50%;
    width: auto;
    /* 为了使按钮居中 */
    margin-top: -22px;
    padding: 16px;
    color: white;
    font-weight: bold;
    font-size: 18px;
    transition: 0.6s ease;
    border-radius: 0 3px 3px 0;
}


/* 定位 "下一张" 按钮靠右 */

.next {
    right: 0;
    border-radius: 3px 0 0 3px;
}

.prev:hover,
.next:hover {
    background-color: rgba(0, 0, 0, 0.8);
}


/* 标题设置属性 */

.text {
    color: #f2f2f2;
    font-size: 15px;
    padding: 8px 12px;
    position: absolute;
    bottom: 8px;
    width: 100%;
    text-align: center;
}


/* 数字 (1/3 等) */

.numbertext {
    color: #f2f2f2;
    font-size: 12px;
    padding: 8px 12px;
    position: absolute;
    top: 0;
}


/* 底部小原点 */

.dot {
    cursor: pointer;
    height: 13px;
    width: 13px;
    margin: 0 2px;
    background-color: #bbb;
    border-radius: 50%;
    display: inline-block;
    transition: background-color 0.6s ease;
}

.active,
.dot:hover {
    background-color: #717171;
}


/* 淡出动画 */

.fade {
    -webkit-animation-name: fade;
    -webkit-animation-duration: 1s;
    animation-name: fade;
    animation-duration: 1s;
}

@-webkit-keyframes fade {
    from {
        opacity: .6
    }
    to {
        opacity: 1
    }
}

@keyframes fade {
    from {
        opacity: .6
    }
    to {
        opacity: 1
    }
}