黑马pink JavaScript学习笔记_Web APIs Day2

事件监听（绑定）

什么是事件？

事件是系统内发生的动作或者发生的事情。比如：用户点击页面上的一个按钮。

什么是事件监听？

就是让程序检测是否有事件产生，一旦有事件触发，就立即调用一个函数做出响应，也称为注册事件

比如：鼠标经过的时候，弹出一个alert“鼠标经过了~”

语法

元素对象.addEventListener('事件类型', 要执行的函数)

事件监听三要素：

事件源：哪个DOM元素被触发了
事件类型：什么方式触发？比如：点击click，鼠标经过mouseenter, 鼠标离开 mouseleave
事件调用的函数：要做什么事情

//鼠标离开，开启定时器
bigBox.addEventListener('mouseleave', function () {
    //先关闭之前的定时器
    clearInterval(timerId);
    //再开启定时器
    timerId = setInterval(function () {
        next.click();
    }, 1000)
})

案例：随机点名案例

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        h2 {
            text-align: center;
        }

        .box {
            width: 600px;
            margin: 50px auto;
            display: flex;
            font-size: 25px;
            line-height: 40px;
        }

        .qs {

            width: 450px;
            height: 40px;
            color: red;

        }

        .btns {
            text-align: center;
        }

        .btns button {
            width: 120px;
            height: 35px;
            margin: 0 50px;
        }
    </style>
</head>

<body>
    <h2>随机点名</h2>
    <div class="box">
        <span>名字是：</span>
        <div class="qs">这里显示姓名</div>
    </div>
    <div class="btns">
        <button class="start">开始</button>
        <button class="end">结束</button>
    </div>

    <script>
        // 数据数组
        let arr = ['马超', '黄忠', '赵云', '关羽', '张飞']
        let timerId = 0;
        let random = 0;

        //开始按钮模块
        const start = document.querySelector(".start");
        const qs = document.querySelector(".qs");

        start.addEventListener("click", function () {
            timerId = setInterval(function () {
                random = Math.floor(Math.random() * arr.length);
                qs.innerHTML = arr[random];
            }, 50)

            if (arr.length === 1) {
                start.disabled = true;
                end.disabled = true;
            }
        })

        //结束按钮模块
        const end = document.querySelector(".end");
        end.addEventListener('click', function () {
            clearInterval(timerId);

            arr.splice(random, 1);
            console.log(arr);

        })
    </script>
</body>

</html>

事件类型

鼠标触发（鼠标事件）

click 鼠标点击
mouseenter 鼠标经过
mouseleave 鼠标离开

表单获得光标（焦点事件）

focus 获得焦点
blur 失去焦点

键盘触发（键盘事件）

keydown 键盘按下触发
keyup 键盘抬起触发

表单输入触发（文本事件）

input 用户输入事件

案例：轮播图点击切换

<!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>轮播图点击切换</title>
  <style>
    * {
      box-sizing: border-box;
    }

    .slider {
      width: 560px;
      height: 400px;
      overflow: hidden;
    }

    .slider-wrapper {
      width: 100%;
      height: 320px;
    }

    .slider-wrapper img {
      width: 100%;
      height: 100%;
      display: block;
    }

    .slider-footer {
      height: 80px;
      background-color: rgb(100, 67, 68);
      padding: 12px 12px 0 12px;
      position: relative;
    }

    .slider-footer .toggle {
      position: absolute;
      right: 0;
      top: 12px;
      display: flex;
    }

    .slider-footer .toggle button {
      margin-right: 12px;
      width: 28px;
      height: 28px;
      appearance: none;
      border: none;
      background: rgba(255, 255, 255, 0.1);
      color: #fff;
      border-radius: 4px;
      cursor: pointer;
    }

    .slider-footer .toggle button:hover {
      background: rgba(255, 255, 255, 0.2);
    }

    .slider-footer p {
      margin: 0;
      color: #fff;
      font-size: 18px;
      margin-bottom: 10px;
    }

    .slider-indicator {
      margin: 0;
      padding: 0;
      list-style: none;
      display: flex;
      align-items: center;
    }

    .slider-indicator li {
      width: 8px;
      height: 8px;
      margin: 4px;
      border-radius: 50%;
      background: #fff;
      opacity: 0.4;
      cursor: pointer;
    }

    .slider-indicator li.active {
      width: 12px;
      height: 12px;
      opacity: 1;
    }
  </style>
</head>

<body>
  <div class="slider">
    <div class="slider-wrapper">
      <img src="./images/slider01.jpg" alt="" />
    </div>
    <div class="slider-footer">
      <p>对人类来说会不会太超前了？</p>
      <ul class="slider-indicator">
        <li class="active"></li>
        <li></li>
        <li></li>
        <li></li>
        <li></li>
        <li></li>
        <li></li>
        <li></li>
      </ul>
      <div class="toggle">
        <button class="prev">&lt;</button>
        <button class="next">&gt;</button>
      </div>
    </div>
  </div>
  <script>
    // 1. 初始数据
    const sliderData = [
      { url: './images/slider01.jpg', title: '对人类来说会不会太超前了？', color: 'rgb(100, 67, 68)' },
      { url: './images/slider02.jpg', title: '开启剑与雪的黑暗传说！', color: 'rgb(43, 35, 26)' },
      { url: './images/slider03.jpg', title: '真正的jo厨出现了！', color: 'rgb(36, 31, 33)' },
      { url: './images/slider04.jpg', title: '李玉刚：让世界通过B站看到东方大国文化', color: 'rgb(139, 98, 66)' },
      { url: './images/slider05.jpg', title: '快来分享你的寒假日常吧~', color: 'rgb(67, 90, 92)' },
      { url: './images/slider06.jpg', title: '哔哩哔哩小年YEAH', color: 'rgb(166, 131, 143)' },
      { url: './images/slider07.jpg', title: '一站式解决你的电脑配置问题！！！', color: 'rgb(53, 29, 25)' },
      { url: './images/slider08.jpg', title: '谁不想和小猫咪贴贴呢！', color: 'rgb(99, 72, 114)' },
    ]

    const img = document.querySelector(".slider-wrapper img");
    const p = document.querySelector('.slider-footer p');
    const prev = document.querySelector(".prev");
    const next = document.querySelector(".next");

    //下一页按钮
    let i = 0;
    next.addEventListener('click', function () {
      i++;

      //重置
      if (i >= sliderData.length) {
        i = 0;
      }

      toggle();
    })


    //上一页按钮
    prev.addEventListener('click', function () {
      i--;

      //重置
      if (i < 0) {
        i = 7;
      }

      toggle();
    })



    //自动播放
    let timerId = setInterval(function () {
      next.click();
    }, 1000)


    //鼠标经过，停止定时器
    const bigBox = document.querySelector('.slider');
    bigBox.addEventListener('mouseenter', function () {
      clearInterval(timerId);
    })


    //鼠标离开，开启定时器
    bigBox.addEventListener('mouseleave', function () {
      //先关闭之前的定时器
      clearInterval(timerId);
      //再开启定时器
      timerId = setInterval(function () {
        next.click();
      }, 1000)
    })



    //抽取公共方法
    function toggle() {
      //设置图片及标题
      img.src = sliderData[i].url;
      p.innerHTML = sliderData[i].title;

      //设置radio
      document.querySelector('.active').classList.remove('active');
      document.querySelector(`.slider-indicator li:nth-child(${i + 1})`).classList.add('active');//这里注意一下，也是i+1

      //设置底部背景色
      document.querySelector('.slider-footer').style.backgroundColor = sliderData[i].color;
    }

  </script>
</body>

</html>

案例：小米搜索框

<!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;
        }

        ul {

            list-style: none;
        }

        .mi {
            position: relative;
            width: 223px;
            margin: 100px auto;
        }

        .mi input {
            width: 223px;
            height: 48px;
            padding: 0 10px;
            font-size: 14px;
            line-height: 48px;
            border: 1px solid #e0e0e0;
            outline: none;
        }

        .mi .search {
            border: 1px solid #ff6700;
        }

        .result-list {
            display: none;
            position: absolute;
            left: 0;
            top: 48px;
            width: 223px;
            border: 1px solid #ff6700;
            border-top: 0;
            background: #fff;
        }

        .result-list a {
            display: block;
            padding: 6px 15px;
            font-size: 12px;
            color: #424242;
            text-decoration: none;
        }

        .result-list a:hover {
            background-color: #eee;
        }
    </style>

</head>

<body>
    <div class="mi">
        <input type="search" placeholder="小米笔记本">
        <ul class="result-list">
            <li><a href="#">全部商品</a></li>
            <li><a href="#">小米11</a></li>
            <li><a href="#">小米10S</a></li>
            <li><a href="#">小米笔记本</a></li>
            <li><a href="#">小米手机</a></li>
            <li><a href="#">黑鲨4</a></li>
            <li><a href="#">空调</a></li>
        </ul>
    </div>
    <script>
        //鼠标悬浮事件
        const input = document.querySelector("input");
        input.addEventListener('focus', function () {
            input.classList.add('search');
            document.querySelector('.result-list').style.display = 'block';
        });

        //鼠标离开事件
        input.addEventListener('blur', function () {
            input.classList.remove('search');
            document.querySelector('.result-list').style.display = 'none';
        });
    </script>
</body>

</html>

案例：评论字数统计

<!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>评论回车发布</title>
  <style>
    .wrapper {
      min-width: 400px;
      max-width: 800px;
      display: flex;
      justify-content: flex-end;
    }

    .avatar {
      width: 48px;
      height: 48px;
      border-radius: 50%;
      overflow: hidden;
      background: url(./images/avatar.jpg) no-repeat center / cover;
      margin-right: 20px;
    }

    .wrapper textarea {
      outline: none;
      border-color: transparent;
      resize: none;
      background: #f5f5f5;
      border-radius: 4px;
      flex: 1;
      padding: 10px;
      transition: all 0.5s;
      height: 30px;
    }

    .wrapper textarea:focus {
      border-color: #e4e4e4;
      background: #fff;
      height: 50px;
    }

    .wrapper button {
      background: #00aeec;
      color: #fff;
      border: none;
      border-radius: 4px;
      margin-left: 10px;
      width: 70px;
      cursor: pointer;
    }

    .wrapper .total {
      margin-right: 80px;
      color: #999;
      margin-top: 5px;
      opacity: 0;
      transition: all 0.5s;
    }

    .list {
      min-width: 400px;
      max-width: 800px;
      display: flex;
    }

    .list .item {
      width: 100%;
      display: flex;
    }

    .list .item .info {
      flex: 1;
      border-bottom: 1px dashed #e4e4e4;
      padding-bottom: 10px;
    }

    .list .item p {
      margin: 0;
    }

    .list .item .name {
      color: #FB7299;
      font-size: 14px;
      font-weight: bold;
    }

    .list .item .text {
      color: #333;
      padding: 10px 0;
    }

    .list .item .time {
      color: #999;
      font-size: 12px;
    }
  </style>
</head>

<body>
  <div class="wrapper">
    <i class="avatar"></i>
    <textarea id="tx" placeholder="发一条友善的评论" rows="2" maxlength="200"></textarea>
    <button>发布</button>
  </div>
  <div class="wrapper">
    <span class="total">0/200字</span>
  </div>
  <div class="list">
    <div class="item" style="display: none;">
      <i class="avatar"></i>
      <div class="info">
        <p class="name">清风徐来</p>
        <p class="text">大家都辛苦啦，感谢各位大大的努力，能圆满完成真是太好了[笑哭][支持]</p>
        <p class="time">2022-10-10 20:29:21</p>
      </div>
    </div>
  </div>


  <script>
    const tx = document.querySelector('#tx');
    const total = document.querySelector('.total');


    tx.addEventListener('focus', function () {
      total.style.opacity = 1;
    })

    tx.addEventListener('blur', function () {
      total.style.opacity = 0;
    })

    tx.addEventListener('input', function () {

      total.innerHTML = `${tx.value.length}/200字`;
    })
  </script>
</body>

</html>

事件对象

事件对象是什么

事件对象也是一个对象，里面有事件触发的相关信息。

如：鼠标点击事件中，事件对象就存储了鼠标点在哪个位置的信息。

使用场景：

可以判断用户按下了哪个按键，不同的按键走不同的代码逻辑

获取事件对象

语法：事件绑定的回调函数的第一个参数就是事件对象。

事件对象常用属性

type
- 获取当前的事件类型
clientX/clientY
- 获取当前光标相对于浏览器可视窗口左上角的位置
offsetX/offsetY
- 获取光标相对于当前DOM元素左上角的位置
key
- 获取用户按下的键盘键的值
- 使用key，现在不提倡使用keyCode

案例：按下回车键，发布评论信息

<!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>评论回车发布</title>
  <style>
    .wrapper {
      min-width: 400px;
      max-width: 800px;
      display: flex;
      justify-content: flex-end;
    }

    .avatar {
      width: 48px;
      height: 48px;
      border-radius: 50%;
      overflow: hidden;
      background: url(./images/avatar.jpg) no-repeat center / cover;
      margin-right: 20px;
    }

    .wrapper textarea {
      outline: none;
      border-color: transparent;
      resize: none;
      background: #f5f5f5;
      border-radius: 4px;
      flex: 1;
      padding: 10px;
      transition: all 0.5s;
      height: 30px;
    }

    .wrapper textarea:focus {
      border-color: #e4e4e4;
      background: #fff;
      height: 50px;
    }

    .wrapper button {
      background: #00aeec;
      color: #fff;
      border: none;
      border-radius: 4px;
      margin-left: 10px;
      width: 70px;
      cursor: pointer;
    }

    .wrapper .total {
      margin-right: 80px;
      color: #999;
      margin-top: 5px;
      opacity: 0;
      transition: all 0.5s;
    }

    .list {
      min-width: 400px;
      max-width: 800px;
      display: flex;
    }

    .list .item {
      width: 100%;
      display: flex;
    }

    .list .item .info {
      flex: 1;
      border-bottom: 1px dashed #e4e4e4;
      padding-bottom: 10px;
    }

    .list .item p {
      margin: 0;
    }

    .list .item .name {
      color: #FB7299;
      font-size: 14px;
      font-weight: bold;
    }

    .list .item .text {
      color: #333;
      padding: 10px 0;
    }

    .list .item .time {
      color: #999;
      font-size: 12px;
    }
  </style>
</head>

<body>
  <div class="wrapper">
    <i class="avatar"></i>
    <textarea id="tx" placeholder="发一条友善的评论" rows="2" maxlength="200"></textarea>
    <button>发布</button>
  </div>
  <div class="wrapper">
    <span class="total">0/200字</span>
  </div>
  <div class="list">
    <div class="item" style="display: none;">
      <i class="avatar"></i>
      <div class="info">
        <p class="name">清风徐来</p>
        <p class="text">大家都辛苦啦，感谢各位大大的努力，能圆满完成真是太好了[笑哭][支持]</p>
        <p class="time">2022-10-10 20:29:21</p>
      </div>
    </div>
  </div>


  <script>
    const tx = document.querySelector('#tx');
    const total = document.querySelector('.total');
    const text = document.querySelector('.text');

    tx.addEventListener('focus', function () {
      total.style.opacity = 1;
    })

    tx.addEventListener('blur', function () {
      total.style.opacity = 0;
    })

    tx.addEventListener('input', function () {
      total.innerHTML = `${tx.value.length}/200字`;
    })


    tx.addEventListener('keyup', function (e) {
      if (e.key == 'Enter') {
        if (tx.value.trim() !== '') {
          document.querySelector('.item').style.display = 'block';
          text.innerHTML = tx.value.trim();
        }
        tx.value = '';
      }
    })
  </script>
</body>

</html>

环境对象

概念：环境对象指的是函数内部特殊的变量this，它代表当前函数运行时所处的环境。

粗略理解：谁调用函数，this指向的就是谁。

回调函数

概念：将函数A作为参数传递给函数B，这个时候，我们就把函数A称为“回调函数”

回调函数的本质还是函数，只不过把它当参数使用。

tx.addEventListener('input', function () {
    console.log("我是一个回调函数");
})

综合案例：Tab栏切换

鼠标经过不同的选项卡，下面动态显示不同的内容。

<!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>tab栏切换</title>
  <style>
    * {
      margin: 0;
      padding: 0;
    }

    .tab {
      width: 590px;
      height: 340px;
      margin: 20px;
      border: 1px solid #e4e4e4;
    }

    .tab-nav {
      width: 100%;
      height: 60px;
      line-height: 60px;
      display: flex;
      justify-content: space-between;
    }

    .tab-nav h3 {
      font-size: 24px;
      font-weight: normal;
      margin-left: 20px;
    }

    .tab-nav ul {
      list-style: none;
      display: flex;
      justify-content: flex-end;
    }

    .tab-nav ul li {
      margin: 0 20px;
      font-size: 14px;
    }

    .tab-nav ul li a {
      text-decoration: none;
      border-bottom: 2px solid transparent;
      color: #333;
    }

    .tab-nav ul li a.active {
      border-color: #e1251b;
      color: #e1251b;
    }

    .tab-content {
      padding: 0 16px;
    }

    .tab-content .item {
      display: none;
    }

    .tab-content .item.active {
      display: block;
    }
  </style>
</head>

<body>
  <div class="tab">
    <div class="tab-nav">
      <h3>每日特价</h3>
      <ul>
        <li><a class="active" href="javascript:;">精选</a></li>
        <li><a href="javascript:;">美食</a></li>
        <li><a href="javascript:;">百货</a></li>
        <li><a href="javascript:;">个护</a></li>
        <li><a href="javascript:;">预告</a></li>
      </ul>
    </div>
    <div class="tab-content">
      <div class="item active"><img src="./images/tab00.png" alt="" /></div>
      <div class="item"><img src="./images/tab01.png" alt="" /></div>
      <div class="item"><img src="./images/tab02.png" alt="" /></div>
      <div class="item"><img src="./images/tab03.png" alt="" /></div>
      <div class="item"><img src="./images/tab04.png" alt="" /></div>
    </div>
  </div>

  <script>
    const as = document.querySelectorAll('a');
    for (let i = 0; i < as.length; i++) {
      as[i].addEventListener('mouseenter', function () {
        // console.log('hello');
        document.querySelector('.tab-nav .active').classList.remove('active');

        this.classList.add('active');


        document.querySelector('.tab-content .active').classList.remove('active');

        document.querySelector(`.tab-content .item:nth-child(${i + 1})`).classList.add('active');
      })
    }
  </script>
</body>

</html>

posted @ 2024-07-23 21:56 千野靑崖阅读(87) 评论(0) 收藏举报

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