要让幻灯片自动切换，可以通过定时器来实现 - 在线编辑器

          <!DOCTYPE html>
<html>
<head>
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <style>
    * {
      box-sizing: border-box
    }

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

    .mySlides {
      display: none
    }
    /* 轮播图容器 */

    .slideshow-container {
      max-width: 1000px;
      position: relative;
      margin: auto;
    }
    /* 上一张和下一张的按钮 */

    .prev,
    .next {
      cursor: pointer;
      position: absolute;
      top: 50%;
      width: auto;
      padding: 16px;
      margin-top: -22px;
      color: white;
      font-weight: bold;
      font-size: 18px;
      transition: 0.6s ease;
      border-radius: 0 3px 3px 0;
    }
    /* 将”下一张“的按钮定位在右边 */

    .next {
      right: 0;
      border-radius: 3px 0 0 3px;
    }
    /* 鼠标移到按钮上，增加一个有点透明的黑色背景 */

    .prev:hover,
    .next:hover {
      background-color: rgba(0, 0, 0, 0.8);
    }
    /* 标题的文本 */

    .text {
      color: #f2f2f2;
      font-size: 15px;
      padding: 8px 12px;
      position: absolute;
      bottom: 8px;
      width: 100%;
      text-align: center;
    }
    /* 图片顺序的文本，(如，1/3) */

    .numbertext {
      color: #f2f2f2;
      font-size: 12px;
      padding: 8px 12px;
      position: absolute;
      top: 0;
    }
    /* 底部的指示按钮 */

    .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;
    }
    /* 淡入淡出的动画 */

    .fade {
      -webkit-animation-name: fade;
      -webkit-animation-duration: 1.5s;
      animation-name: fade;
      animation-duration: 1.5s;
    }

    @-webkit-keyframes fade {
      from {
        opacity: .4
      }
      to {
        opacity: 1
      }
    }

    @keyframes fade {
      from {
        opacity: .4
      }
      to {
        opacity: 1
      }
    }
  </style>
</head>
<body>

  <h2>轮播图自动切换</h2>
  <p>每两秒更改到下一张图片：</p>

  <div class="slideshow-container">

    <div class="mySlides fade">
      <div class="numbertext">1 / 3</div>
      <img src="https://image-10001577.image.myqcloud.com/upload/3/20170428/14933734123710.jpg" style="width:100%">
      <div class="text">标题1</div>
    </div>

    <div class="mySlides fade">
      <div class="numbertext">2 / 3</div>
      <img src="https://image-10001577.image.myqcloud.com/upload/3/20170428/1493373435281.jpg" style="width:100%">
      <div class="text">标题2</div>
    </div>

    <div class="mySlides fade">
      <div class="numbertext">3 / 3</div>
      <img src="https://image-10001577.image.myqcloud.com/upload/3/20170428/14933734551830.jpg" style="width:100%">
      <div class="text">标题3</div>
    </div>

  </div>
  <br>

  <div style="text-align:center">
    <span class="dot"></span>
    <span class="dot"></span>
    <span class="dot"></span>
  </div>

  <script>
    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";
      // 每两秒展示下一张图片
      setTimeout(showSlides, 2000);
    }
  </script>

</body>
</html>
        