简单的选显卡和懒加载

选项卡

<!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>选项卡</title>
    <style>
      * {
        margin: 0;
        padding: 0;
      }
      li {
        list-style: none;
      }
      .nav {
        display: flex;
      }
      .nav li {
        margin-bottom: 0;
        width: 100px;
        height: 50px;
        text-align: center;
        line-height: 50px;
      }
      .content {
        background-color: red;
        width: 100%;
        display: none;
        height: 150px;
      }
      .active {
        display: block;
        background-color: red;
      }
    </style>
  </head>
  <body>
    <div style="width: 300px">
      <ul class="nav">
        <li data-index="1" class="active">动漫</li>
        <li data-index="2">电视剧</li>
        <li data-index="3">电影</li>
      </ul>
      <ul class="content active" data-index="1">
        <li>火影忍者</li>
        <li>斗罗大陆</li>
        <li>斗破苍穹</li>
      </ul>
      <ul class="content" data-index="2">
        <li>对不起我爱你</li>
        <li>天龙八部</li>
        <li>神雕侠侣</li>
      </ul>
      <ul class="content" data-index="3">
        <li>金瓶梅</li>
        <li>3D肉蒲团</li>
        <li>蜜桃成熟时</li>
      </ul>
    </div>
    <script>
      let nav = document.querySelector(".nav");
      let c = nav.children;
      let d = document.querySelectorAll(".content");
      let b = (nav.onmouseover = function (ev) {
        let a = ev.target;
        [...c].forEach((item) => item.classList.remove("active"));
        a.classList.add("active");
        [...d].filter(function (n) {
          n.classList.remove("active");
          if (n.dataset.index == a.dataset.index) {
            n.classList.add("active");
          }
        });
      });
    </script>
  </body>
</html>

懒加载

<!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>选项卡</title>
    <style>
      .container {
        height: 2000px;
      }
      .container > img {
        position: absolute;
        top: 1000px;
      }
    </style>
  </head>
  <body>
    <div class="container">
      <img data-src="huoying.jpg" alt="" />
    </div>
    <script>
      //获取图片元素
      let imgs = document.querySelector(".container > img");
      // 元素相对于可视区的位置
      // let rect = imgs.getBoundingClientRect();
      // 窗口可视区高度
      let viewLight = window.innerHeight;
      window.onscroll = function () {
        if (imgs.getBoundingClientRect().top < viewLight) {
          imgs.src = imgs.dataset.src;
        }
      };
    </script>
  </body>
</html>

选项卡

懒加载

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