导航栏下划线跟随

1.html代码

<ul>
    <li>首页</li>
    <li>今日要闻</li>
    <li>风景图片</li>
    <li>天气预报</li>
    <li>我的日记</li>
</ul>

2.css代码

  <style>
        ul {
            display: flex;
            position: absolute;
            width: 800px;
            top: 10%;
            left: 50%;
            transform: translate(-50%, -50%);
            list-style: none;
        }

        li {
            position: relative;
            padding: 20px;
            font-size: 24px;
            color: #000;
            line-height: 1;
            transition: 0.2s all linear;
            cursor: pointer;
        }

        li::before {
            content: "";
            position: absolute;
            top: 0;
            left: 100%;
            width: 0;
            height: 100%;
            border-bottom: 2px solid #000;
            transition: 0.2s all linear;
        }

        li:hover::before {
            width: 100%;
            top: 0;
            left: 0;
            transition-delay: 0.1s;
            border-bottom-color: #000;
            z-index: -1;
        }

        li:hover ~ li::before {
            left: 0;
        }

        li:active {
            background: #000;
            color: #fff;
        }

3.最终效果如图，鼠标经过的时候会出现下划线