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js学习：第18章 JS实战选项卡、懒加载、轮播图
王小飞
Original
993 people have browsed it

轮播图：

代码：

  1. <!DOCTYPE html>
  2. <html lang="en">
  3.   <head>
  4.     <meta charset="UTF-8" />
  5.     <title>首页轮播图</title>
  6.     <style>
  7.       ul,
  8.       li {
  9.         margin: 0;
  10.         padding: 0;
  11.         list-style: none;
  12.       }
  14.       .box {
  15.         /*定位父级*/
  16.         position: relative;
  17.         width: 1000px;
  18.         height: 350px;
  19.         margin: 0 auto;
  20.       }
  22.       .box .slider {
  23.         width: 1000px;
  24.         height: 350px;
  25.         display: none;
  26.       }
  28.       .box .slider.active {
  29.         display: block;
  30.       }
  32.       .box .point-list {
  33.         position: absolute;
  34.         /*绝对定位的环境下的水平居中方式*/
  35.         left: 50%;
  36.         margin-left: -38px;
  37.         top: 310px;
  38.       }
  40.       .box .point-list .point {
  41.         display: inline-block;
  42.         width: 12px;
  43.         height: 12px;
  44.         margin: 0 5px;
  45.         background-color: white;
  46.         border-radius: 100%;
  47.       }
  49.       .box .point-list .point.active {
  50.         background-color: black;
  51.       }
  53.       .box .point-list .point:hover {
  54.         cursor: pointer;
  55.       }
  57.       .skip {
  58.         position: absolute;
  59.         top: 140px;
  60.         display: inline-block;
  61.         width: 40px;
  62.         height: 80px;
  63.         text-align: center;
  64.         line-height: 80px;
  65.         background-color: lightgray;
  66.         color: white;
  67.         opacity: 0.2;
  68.         font-size: 36px;
  69.       }
  71.       .box .prev {
  72.         left: 0;
  73.       }
  75.       .box .next {
  76.         right: 0;
  77.       }
  79.       .box .skip:hover {
  80.         cursor: pointer;
  81.         opacity: 0.5;
  82.         color: black;
  83.       }
  84.     </style>
  85.   </head>
  87.   <body>
  88.     <div class="box">
  89.       <img
  90.         src="banner/banner1.jpg"
  91.         alt=""
  92.         data-index="1"
  93.         class="slider active"
  94.       />
  95.       <img src="banner/banner2.jpg" alt="" data-index="2" class="slider" />
  96.       <img src="banner/banner3.jpg" alt="" data-index="3" class="slider" />
  98.       <div class="point-list">
  99.         <!-- <span class="point active" data-index="1"></span>
  100.         <span class="point" data-index="2"></span>
  101.         <span class="point" data-index="3"></span> -->
  102.       </div>
  104.       <span class="skip prev">&lt;</span>
  105.       <span class="skip next">&gt;</span>
  106.     </div>
  108.     <script>
  109.       var cl = console.log.bind(console);
  110.       // 轮播图片组
  111.       var imgs = document.querySelectorAll("img");
  113.       var pointList = document.querySelector(".point-list");
  115.       // 动态生成小圆点
  116.       imgs.forEach(function (img, index) {
  117.         var span = document.createElement("span");
  118.         if (index === 0) span.classList.add("point", "active");
  119.         span.classList.add("point");
  120.         // 将小圆点与当前显示的图片的索引进行关联
  121.         span.dataset.index = img.dataset.index;
  123.         pointList.appendChild(span);
  124.       });
  126.       // 为了正确的设置小圆点高亮, 这里需要获取到所有的小圆点
  127.       var points = document.querySelectorAll(".point");
  129.       // 事件代理/委托: 给小圆点添加点击事件
  130.       pointList.addEventListener(
  131.         "click",
  132.         function (ev) {
  133.           cl(ev.target);
  134.           imgs.forEach(function (img) {
  135.             if (img.dataset.index === ev.target.dataset.index) {
  136.               imgs.forEach(function (img) {
  137.                 img.classList.remove("active");
  138.               });
  139.               // 设置当前图片的激活样式
  140.               img.classList.add("active");
  142.               // 公共函数: 设置小圆点当前的高亮, 必须与图片一一对应, 同步
  143.               setPointActive(img.dataset.index);
  144.             }
  145.           });
  146.         },
  147.         false
  148.       );
  150.       // 公共函数:setPointActive
  151.       function setPointActive(imgIndex) {
  152.         // 清除原来的所有的小圆点上的高亮
  153.         points.forEach(function (point) {
  154.           point.classList.remove("active");
  155.         });
  157.         points.forEach(function (point) {
  158.           if (point.dataset.index === imgIndex) point.classList.add("active");
  159.         });
  160.       }
  162.       // 获取翻页按钮
  163.       var skip = document.querySelectorAll(".skip");
  165.       // 添加事件
  166.       skip.item(0).addEventListener("click", skipImg, false);
  167.       skip.item(1).addEventListener("click", skipImg, false);
  169.       // 翻页事件回调skipImg
  170.       function skipImg(ev) {
  171.         // 遍历并找到当前正在显示的图片
  172.         var currentImg = null;
  173.         imgs.forEach(function (img) {
  174.           if (img.classList.contains("active")) currentImg = img;
  175.         });
  177.         // 1. 判断是否是点击了显示前一张?
  178.         if (ev.target.classList.contains("prev")) {
  179.           currentImg.classList.remove("active");
  180.           currentImg = currentImg.previousElementSibling;
  181.           cl(currentImg);
  183.           // 如果存在前一张
  184.           if (currentImg !== null && currentImg.nodeName === "IMG")
  185.             // 将当前图片显示
  186.             currentImg.classList.add("active");
  187.           else {
  188.             //否则就显示最后一张,形成循环
  189.             currentImg = imgs[imgs.length - 1];
  190.             currentImg.classList.add("active");
  191.           }
  192.         }
  194.         // 2. 判断是否是点击了显示下一张?
  195.         if (ev.target.classList.contains("next")) {
  196.           currentImg.classList.remove("active");
  197.           currentImg = currentImg.nextElementSibling;
  198.           cl(currentImg);
  200.           // 如果存在前一张
  201.           if (currentImg !== null && currentImg.nodeName === "IMG")
  202.             // 将当前图片显示
  203.             currentImg.classList.add("active");
  204.           else {
  205.             //否则就显示最后一张,形成循环
  206.             currentImg = imgs[0];
  207.             currentImg.classList.add("active");
  208.           }
  209.         }
  211.         // 公共函数: 设置小圆点当前的高亮, 必须与图片一一对应, 同步
  212.         setPointActive(currentImg.dataset.index);
  213.       }
  215.       var box = document.querySelector(".box");
  217.       var timer = null;
  219.       // 1. 当鼠标移出轮播图区域时, 启动定时器,每2秒自动切换图片
  220.       box.addEventListener("mouseout", startTimer, false);
  221.       // 2. 当鼠标移入轮播图区域时,清除定时器,由用户点击操作
  222.       box.addEventListener("mouseover", clearTimer, false);
  224.       // 启动定时器
  225.       function startTimer() {
  226.         var click = new Event("click");
  227.         //setInterval(): 间歇式执行
  228.         setInterval(function () {
  229.           skip.item(1).dispatchEvent(click);
  230.         }, 6000);
  231.       }
  233.       // 清除定时器
  234.       function clearTimer() {
  235.         clearInterval(timer);
  236.       }
  237.     </script>
  238.   </body>
  239. </html>

效果：

动态：

选项卡：

代码：

  1. <!DOCTYPE html>
  2. <html lang="en">
  3.   <head>
  4.     <meta charset="UTF-8" />
  5.     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  6.     <title>选项卡</title>
  7.     <style>
  8.       * {
  9.         margin: 0;
  10.         padding: 0;
  11.       }
  12.       a {
  13.         text-decoration: none;
  14.         color: #555;
  15.       }
  16.       a:hover {
  17.         text-decoration: underline;
  18.         color: red;
  19.       }
  20.       li {
  21.         list-style: none;
  22.       }
  23.       li:hover {
  24.         cursor: default;
  25.       }
  26.       .tabs {
  27.         width: 300px;
  28.         height: 300px;
  29.         margin: 30px;
  30.         background-color: #ddd;
  32.         display: flex;
  33.         flex-direction: column;
  34.       }
  36.       .tab {
  37.         height: 36px;
  38.         display: flex;
  39.       }
  40.       .tab li {
  41.         flex: auto;
  42.         text-align: center;
  43.         line-height: 36px;
  44.         background-color: #fff;
  45.       }
  46.       .tab li.active {
  47.         background-color: #ddd;
  48.       }
  50.       /* 默认所有选项卡只有一个显示,其它隐藏 */
  51.       .item {
  52.         padding: 20px;
  53.         display: none;
  54.       }
  55.       .item.active {
  56.         display: block;
  57.       }
  58.     </style>
  59.   </head>
  60.   <body>
  61.     <div class="tabs">
  62.       <!-- 导航 -->
  63.       <ul class="tab">
  64.         <li class="active" data-index="1">公司动态</li>
  65.         <li data-index="2">行业动态</li>
  66.         <li data-index="3">技术支持</li>
  67.       </ul>
  69.       <!-- 详情1 -->
  70.       <ul class="item active" data-index="1">
  71.         <li><a href="">2020年春节放假通知</a></li>
  72.         <li><a href="">五一超级特惠活动</a></li>
  73.         <li><a href="">2019年春节放假通知</a></li>
  74.       </ul>
  76.       <!-- 详情2 -->
  77.       <ul class="item" data-index="2">
  78.         <li><a href="">小型冷库的设计要求是怎么样的</a></li>
  79.         <li><a href="">冷库实现节能的方法有哪些</a></li>
  80.         <li><a href="">冷库出现堵冰现象怎么办</a></li>
  81.       </ul>
  83.       <!-- 详情2 -->
  84.       <ul class="item" data-index="3">
  85.         <li><a href="">安装小型冷库对保存水果的</a></li>
  86.         <li><a href="">冷库安装后出现裂缝是怎么</a></li>
  87.         <li><a href="">冷库安装后，怎么样发挥冷库的作用？</a></li>
  88.       </ul>
  89.     </div>
  91.     <script>
  92.       var cl = console.log.bind(console);
  94.       // 导航:事件委托
  95.       var tab = document.querySelector(".tab");
  96.       // 列表
  97.       var items = document.querySelectorAll(".item");
  99.       // 给导航绑定点击事件
  100.       tab.addEventListener("click", show, false);
  102.       // 给导航绑定鼠标移动事件
  103.       tab.addEventListener("mouseover", show, false);
  104.       // 事件回调函数
  105.       function show(ev) {
  106.         cl(ev.target);
  107.         // data-index
  108.         // cl(ev.target.dataset.index);
  109.         // 1. 清空导航原有的激活
  110.         ev.target.parentNode.childNodes.forEach(function (item) {
  111.           if (item.nodeType === 1) item.classList.remove("active");
  112.         });
  114.         // 2. 将当前用户正在点击的导航设置为激活
  115.         ev.target.classList.toggle("active");
  117.         // 3. 清空列表的原有激活
  118.         items.forEach(function (item) {
  119.           item.classList.remove("active");
  120.         });
  122.         // 4. 在列表中查询data-index与导航的data-index相等的内容,将它设置为激活
  123.         items.forEach(function (item) {
  124.           if (item.dataset.index === ev.target.dataset.index)
  125.             item.classList.add("active");
  126.         });
  127.       }
  128.     </script>
  129.   </body>
  130. </html>

效果：

Correcting teacher：天蓬老师天蓬老师

Correction status：qualified

Teacher's comments：这几个案例写完, 是不是对自己又充满了信心
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