基于JavaScript实现简单的轮播图

本文实例为大家分享了JavaScript实现简单的轮播图的具体代码，供大家参考，具体内容如下

js轮播图实现思路

1、先获取元素盒子左右按钮
2、鼠标经过显示/隐藏左右侧按钮
3、动态生成小圆圈、添加自定义属性
4、小圆圈点击事件添加current类名
5、添加动画事件 animate 等于 -索引号*focusWidth
6、克隆第一张图片到最后面
7、添加右侧/左侧按钮点击事件
8、设置定时器手动调用右侧按钮点击事件

html代码部分

<!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>
 <link rel="stylesheet" href="css/index.css" >
 <script src="js/index.js"></script>
</head>

<body>
 <div class="focus">
 <a href="javascript:;" class="arrow_r">></a>
 <a href="javascript:;" class="arrow_l">
  <</a>
  <ul>
   <li>
   <a href=""><img src="images/focus.jpg" alt=""></a>
   </li>
   <li>
   <a href=""><img src="images/focus1.jpg" alt=""></a>
   </li>
   <li>
   <a href=""><img src="images/focus2.jpg" alt=""></a>
   </li>
   <li>
   <a href=""><img src="images/focus3.jpg" alt=""></a>
   </li>
  </ul>
  <ol class="circle">
  </ol>
 </div>
</body>

</html>

css样式部分

* {
 padding: 0;
 margin: 0;
 }
 
 li {
 list-style: none;
 }
 
 img {
 border: 0;
 vertical-align: top;
 }
 
 a {
 text-decoration: none;
 }
 
 .focus {
 position: relative;
 width: 721px;
 height: 455px;
 margin: 100px auto;
 overflow: hidden;
 }
 
 .focus ul {
 position: absolute;
 top: 0;
 left: 0;
 width: 600%;
 }
 
 .focus ul li {
 float: left;
 }
 
 .arrow_r,
 .arrow_l {
 display: none;
 position: absolute;
 top: 50%;
 transform: translateY(-50%);
 width: 40px;
 height: 40px;
 line-height: 40px;
 text-align: center;
 font-size: 24px;
 background: rgba(0, 0, 0, .2);
 color: #fff;
 z-index: 1;
 }
 
 .arrow_r {
 right: 0;
 }
 
 .circle {
 position: absolute;
 bottom: 10px;
 left: 50px;
 }
 
 .circle li {
 float: left;
 width: 8px;
 height: 8px;
 border: 2px solid rgba(255, 255, 255, .5);
 border-radius: 50%;
 margin: 0 3px;
 cursor: pointer;
 }
 
 .current {
 background-color: #fff;
 }

javascript部分

window.addEventListener('load', function() {
 //获取元素
 var focus = document.querySelector('.focus');
 var arrow_r = document.querySelector('.arrow_r');
 var arrow_l = document.querySelector('.arrow_l');
 var focusWidth = focus.offsetWidth;
 // 鼠标经过focus盒子 显示/隐藏 左右侧按钮 暂停轮播
 focus.addEventListener('mouseenter', function() {
 arrow_r.style.display = 'block';
 arrow_l.style.display = 'block';
 clearInterval(timer);
 timer = null;
 });
 focus.addEventListener('mouseleave', function() {
 arrow_r.style.display = 'none';
 arrow_l.style.display = 'none';
 timer = setInterval(function() {
  //调用点击事件
  arrow_r.click();
 }, 2000);
 });
 //动态生成小圆圈
 var ul = focus.querySelector('ul');
 var ol = focus.querySelector('.circle');
 for (var i = 0; i < ul.children.length; i++) {
 var li = document.createElement('li');
 li.setAttribute('index', i);
 ol.appendChild(li);
 //小圆圈点击事件
 li.addEventListener('click', function() {
  for (var i = 0; i < ol.children.length; i++) {
  ol.children[i].className = '';
  }
  var index = this.getAttribute('index');
  num = index;
  circle = index;
  this.className = 'current';
  animate(ul, -index * focusWidth);
 })
 }
 ol.children[0].className = 'current';
 //克隆第一张图片放到最后一张
 var fis = ul.children[0].cloneNode(true);
 ul.appendChild(fis);
 //右侧按钮点击事件
 var num = 0;
 var circle = 0;
 arrow_r.addEventListener('click', function() {
 if (num === ul.children.length - 1) {
  ul.style.left = 0;
  num = 0;
 }
 num++;
 animate(ul, -num * focusWidth);
 circle++;
 if (circle === ul.children.length - 1) {
  circle = 0;
 }
 for (var i = 0; i < ol.children.length; i++) {
  ol.children[i].className = '';
 }
 ol.children[circle].className = 'current';
 });
 //左侧按钮点击事件
 arrow_l.addEventListener('click', function() {
 if (num == 0) {
  num = ul.children.length - 1;
  ul.style.left = -num * focusWidth + 'px';

 }
 num--;
 animate(ul, -num * focusWidth);
 circle--;
 circle = circle < 0 ? ol.children.length - 1 : circle;
 // 调用函数
 circleChange();
 });
 //清除其余小圆圈的current类名
 function circleChange() {
 for (var i = 0; i < ol.children.length; i++) {
  ol.children[i].className = '';
 }
 // 留下当前的小圆圈的current类名
 ol.children[circle].className = 'current';
 }
 //动画函数
 function animate(obj, target, callback) {
 clearInterval(obj.timer);
 obj.timer = setInterval(function() {
  var step = (target - obj.offsetLeft) / 10;
  step = step > 0 ? Math.ceil(step) : Math.floor(step);
  if (obj.offsetLeft == target) {
  clearInterval(obj.timer);
  callback && callback();
  }
  obj.style.left = obj.offsetLeft + step + 'px';

 }, 15);
 }
 //自动轮播放轮播图
 var timer = setInterval(function() {
 //调用点击事件
 arrow_r.click();
 }, 2000);
});

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持呐喊教程。

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