JavaScript实现PC端横向轮播图

<div id="swiper">
 <ul class="list">
  <li><img src="img/9.jpg" alt=""></li>
  <!-- 最后一张 -->
  <li><img src="img/2.jpg" alt=""></li>
  <li><img src="img/3.jpg" alt=""></li>
  <li><img src="img/4.jpg" alt=""></li>
  <li><img src="img/6.jpg" alt=""></li>
  <li><img src="img/9.jpg" alt=""></li>
  <!-- 第一张 -->
  <li><img src="img/2.jpg" alt=""></li>
 </ul>
 <span class="btn-left">&lt;</span>
 <span class="btn-right">&gt;</span>
 <ul class="points">
  <li class="current"></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
</ul>

<style type="text/css">
 * {
  margin: 0;
  padding: 0;
 }
 
 ul,
 li {
  list-style: none;
 }
 
 a {
  text-decoration: none;
 }
 
 img {
  display: block;
 }
 
 input {
  outline: none;
 }
 
 .clearFix:after {
  content: '';
  display: block;
  clear: both;
 }
 /*禁止系统滚动条*/
 
 html,
 body {
  height: 100%;
  overflow: hidden;
 }
 
 #swiper {
  position: relative;
  width: 1000px;
  height: 500px;
  background: green;
  margin: 50px auto 0;
  overflow: hidden;
 }
 
 #swiper .list {
  position: absolute;
  left: -1000px;
  top: 0;
  width: 7000px;
  overflow: hidden;
 }
 
 #swiper .list>li {
  float: left;
  width: 1000px;
  height: 500px;
 }
 
 #swiper .list>li img {
  width: 100%;
  height: 100%;
 }
 
 #swiper span {
  position: absolute;
  /* left: 0; */
  top: 40%;
  transform: translateY(-50%);
  width: 80px;
  height: 100px;
  background: rgba(0, 0, 0, 0.5);
  font-size: 50px;
  color: white;
  font-weight: bold;
  padding-top: 30px;
  text-align: center;
  opacity: 0;
  transition: opacity 1s;
  cursor: pointer;
 }
 
 #swiper:hover span {
  opacity: 1;
 }
 
 #swiper .btn-left {
  left: 0;
 }
 
 #swiper .btn-right {
  right: 0;
 }
 
 #swiper .points {
  position: absolute;
  left: 40%;
  transform: translateX(-50%);
  bottom: 20px;
  /* width: 300px; */
 }
 
 #swiper .points>li {
  width: 30px;
  height: 30px;
  background: rgba(0, 0, 0, 0.5);
  border-radius: 50%;
  float: left;
  margin: 0 5px;
 }
 
 #swiper .points .current {
  background: red;
 }
</style>

<script>
 window.onload = function() {
  // 获取变量
  var swiper = document.querySelector('#swiper');
  var list = document.querySelector('#swiper .list');
  var liNodes = document.querySelectorAll('#swiper .list>li');
  var btnNodes = document.querySelectorAll('#swiper span');
  // 切换一张需要的总时长
  var timeAll = 1000;
  // 每走一步需要的时长
  var timeStep = 20;
  var timer = null;
  // 小圆点
  var icons = document.querySelectorAll('#swiper>.points li');
  var isMove = false;
  var autoTimer = null;

  // 鼠标进入banner
  swiper.onmouseenter = function() {
  // 清除定时器
  clearInterval(autoTimer);
  }

  // 鼠标离开banner
  swiper.onmouseleave = function() {
  // 打开自动轮播定时器
  autoRun();
  }

  // 点击按钮切换图片
  // 右按钮
  btnNodes[1].onclick = function() {
  // 图片且切换函数
  move(true);
  }

  // 左按钮
  btnNodes[0].onclick = function() {
  // 图片切换函数
  move(false);
  }

  // 图片切换函数
  function move(flag) {
  // 保证定时器只开一个，不会堆砌
  if (isMove) {
   return;
  }
  isMove = true;


  // 区分flag参数，boolean是左右图片切换
  if (typeof flag == 'boolean') {
   if (flag) {
   var elementDistance = -1000;
   } else {
   var elementDistance = 1000;
   }
  } else {
   var elementDistance = flag - list.offsetLeft;
  }

  // 每次点击后，ul所走的距离
  var elementLast = list.offsetLeft + elementDistance;
  // 每走一小步的距离
  var step = elementDistance / (timeAll / timeStep);

  timer = setInterval(function() {
   var left = list.offsetLeft + step;
   if (left == elementLast) {
   // 走的的距离等于最终的位置
   clearInterval(timer);
   if (left == -6000) {
    left = -1000;
   } else if (left == 0) {
    left = -5000;
   }
   isMove = false;
   }
   // 设置样式
   list.style.left = left + 'px';
  }, timeStep);

  // 小圆点切换逻辑
  for (var i = 0; i < icons.length; i++) {
   icons[i].className = '';
  }

  // 小圆点切换
  var index = elementLast / -1000 - 1;
  if (index > 4) {
   index = 0;
  } else if (index < 0) {
   index = 4;
  }
  icons[index].className = 'current';
  console.log(icons);
  //让自动轮播和点击后下标保持统一
  autoIndex = index + 1;
  }

  // 点击小圆点逻辑
  for (var i = 0; i < icons.length; i++) {
  icons[i].index = i;
  icons[i].onclick = function() {
   // 拿小圆点下标，求显示图片的下标，再求显示图片位置
   move((this.index + 1) * -1000);
  }
  }

  // 自动轮播逻辑
  var autoIndex = 1;
  autoRun();

  function autoRun() {
  autoTimer = setInterval(function() {
   autoIndex++;
   move(autoIndex * -1000);
   if (autoIndex == 6) {
   autoIndex = 1;
   }
  }, 2000);
  }
 }
</script>