JS基础教程：2023.3.26第二十八天-JavaScript web APIs Dom事件进阶

前言

记录时间：2023.3.26

坚持的第二十八天

JavaScript从入门到精通

学习javascript时间历程记录打卡

晚上8:30到22：30

JS-Dom事件进阶总结

完成代码练习

1.页面尺寸事件

<!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>
  <style>
    div {
      display: inline-block;
      /* width: 200px; */
      height: 200px;
      background-color: pink;
      padding: 10px;
      border: 20px solid red;
    }
  </style>
</head>

<body>
  <div>123123123123123123123123123123123123123</div>
  <script>
    const div = document.querySelector('div')
    console.log(div.clientWidth)
    // resize 浏览器窗口大小发生变化的时候触发的事件
    window.addEventListener('resize', function () {
      console.log(1)
    })
  </script>
</body>

</html>

2.offsetLeft

<!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>
  <style>
    div {
      position: relative;
      width: 200px;
      height: 200px;
      background-color: pink;
      margin: 100px;
    }

    p {
      width: 100px;
      height: 100px;
      background-color: purple;
      margin: 50px;
    }
  </style>
</head>

<body>
  <div>
    <p></p>
  </div>
  <script>
    const div = document.querySelector('div')
    const p = document.querySelector('p')
    // console.log(div.offsetLeft)
    // 检测盒子的位置  最近一级带有定位的祖先元素
    console.log(p.offsetLeft)
  </script>
</body>

</html>

3.仿新浪固定头部

<!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>
    <style>
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        .content {
            overflow: hidden;
            width: 1000px;
            height: 3000px;
            background-color: pink;
            margin: 0 auto;
        }

        .backtop {
            display: none;
            width: 50px;
            left: 50%;
            margin: 0 0 0 505px;
            position: fixed;
            bottom: 60px;
            z-index: 100;
        }

        .backtop a {
            height: 50px;
            width: 50px;
            background: url(./images/bg2.png) 0 -600px no-repeat;
            opacity: 0.35;
            overflow: hidden;
            display: block;
            text-indent: -999em;
            cursor: pointer;
        }

        .header {
            position: fixed;
            top: -80px;
            left: 0;
            width: 100%;
            height: 80px;
            background-color: purple;
            text-align: center;
            color: #fff;
            line-height: 80px;
            font-size: 30px;
            transition: all .3s;
        }

        .sk {
            width: 300px;
            height: 300px;
            background-color: skyblue;
            margin-top: 500px;
        }
    </style>
</head>

<body>
    <div class="header">我是顶部导航栏</div>
    <div class="content">
        <div class="sk">秒杀模块</div>
    </div>
    <div class="backtop">
        <img src="./images/close2.png" >
        <a href="javascript:;"></a>
    </div>
    <script>
        const sk = document.querySelector('.sk')
        const header = document.querySelector('.header')
        // 1. 页面滚动事件
        window.addEventListener('scroll', function () {
            // 当页面滚动到 秒杀模块的时候，就改变 头部的 top值
            // 页面被卷去的头部 >=  秒杀模块的位置 offsetTop
            const n = document.documentElement.scrollTop
            // if (n >= sk.offsetTop) {
            //     header.style.top = 0
            // } else {
            //     header.style.top = '-80px'
            // }
            header.style.top = n >= sk.offsetTop ? 0 : '-80px'
        })
    </script>
</body>

</html>

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