DOM（二）：事件监听、事件类型、事件对象、环境对象、回调函数、Tab栏切换
1、事件监听
1）基础
元素对象就是事件源
<body><button>点</button><script>const btn = document.querySelector('button')btn.addEventListener('click', function () {alert(`Hello World!`)})</script>
</body>2） 案例：关闭广告
<!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>.box {position: relative;width: 200px;height: 200px;background-color: skyblue;margin: 100px auto;line-height: 200px;text-align: center;}.close {position: absolute;top: 4px;right: 4px;width: 20px;height: 20px;background-color: #fff;text-align: center;line-height: 20px;font-size: 16px;cursor: pointer;}</style>
</head><body><div class="box">ad<div class="close">X</div></div><script>const box = document.querySelector('.box')const close = document.querySelector('.close')close.addEventListener('click', function () {box.style.display = 'none'})</script>
</body></html>3）案例：随机点名
<!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: blue;}.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>const arr = ['张三', '李四', '王五', '赵六', '钱七']let timerID = 0let random = 0const qs = document.querySelector('.qs')// start模块const start = document.querySelector('.start')// 添加点击事件start.addEventListener('click', function () {// 点击开始按钮后，禁用开始按钮，防止多线程问题；结束按钮同理start.disabled = trueend.disabled = falsetimerID = setInterval(function () {random = parseInt(Math.random() * arr.length)// console.log(arr[random])qs.innerHTML = arr[random]}, 100)// 数组中只有一个值时，禁用按钮if (arr.length === 1) {start.disabled = trueend.disabled = true}})// end模块const end = document.querySelector('.end')end.addEventListener('click', function () {start.disabled = falseend.disabled = trueclearInterval(timerID)arr.splice(random, 1)})</script>
</body></html>4）事件监听版本
2、事件类型
1）基础
2）案例：完整轮播图
<!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>* {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"><</button><button class="next">></button></div></div></div><script>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 footer = document.querySelector('.slider-footer')let i = 0 // 控制图片播放// 右侧按钮模块const next = document.querySelector('.next')next.addEventListener('click', function () {i++if (i >= sliderData.length) i = 0toggle()})//左侧按钮模块const prev = document.querySelector('.prev')prev.addEventListener('click', function () {i--if (i < 0) i = sliderData.length - 1toggle()})function toggle() {img.src = sliderData[i].urlp.innerHTML = sliderData[i].titlefooter.style.backgroundColor = sliderData[i].color// 更换小圆点document.querySelector('.slider-indicator .active').classList.remove('active')document.querySelector(`.slider-indicator li:nth-child(${i + 1})`).classList.add('active')}//自动播放模块let timerID = setInterval(function () {// 利用js自动调用点击事件next.click() //右侧按钮点击事件}, 1000)//鼠标经过大盒子，停止定时器const slider = document.querySelector('.slider')slider.addEventListener('mouseenter', function () {clearInterval(timerID)})//鼠标离开，打开定时器slider.addEventListener('mouseleave', function () {timerID = setInterval(function () {// 利用js自动调用点击事件next.click() //右侧按钮点击事件}, 3000)})</script>
</body></html>3）案例：搜素框
<!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;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>// 属性选择器const input = document.querySelector('[type=search]')const ul = document.querySelector('.result-list')// 监听事件 获得焦点input.addEventListener('focus', function () {ul.style.display = 'block'input.classList.add('search')})input.addEventListener('blur', function () {ul.style.display = 'none'input.classList.remove('search')})</script>
</body></html>4）案例：发布评论
CSS小知识：
<style>input {width: 200px;/* height: 200px; */transition: all .3s;}/* CSS 选择器 focus伪类选择器 获得焦点*/input:focus {width: 300px;}</style><body><input type="text">
</body>
<!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')// 文本域获得焦点，total显示tx.addEventListener('focus', function () {total.style.opacity = 1})// 文本域失去焦点，total隐藏tx.addEventListener('blur', function () {total.style.opacity = 0})//检测用户输入 输入内容长度tx.addEventListener('input', function () {total.innerHTML = `${tx.value.length}/200字`})</script>
</body></html>3、事件对象
1）获取事件对象
2）案例：回车评论
字符串去除左右空格：
<script>const str = ' aaa 'console.log(str.trim());
</script>
<!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">2025-9-25 21:29:21</p></div></div></div><script>const tx = document.querySelector('#tx')const total = document.querySelector('.total')const item = document.querySelector('.item')const text = document.querySelector('.text')// 文本域获得焦点，total显示tx.addEventListener('focus', function () {total.style.opacity = 1})// 文本域失去焦点，total隐藏tx.addEventListener('blur', function () {total.style.opacity = 0})//检测用户输入 输入内容长度tx.addEventListener('input', function () {total.innerHTML = `${tx.value.length}/200字`})// 回车发布评论 键盘事件tx.addEventListener('keyup', function (e) {// e.key获得具体按键if (e.key == 'Enter') {if (tx.value.trim() !== '') {item.style.display = 'block'text.innerHTML = tx.value}tx.value = ''total.innerHTML = `0/200字`}})</script>
</body></html>4、环境对象
<script>function fn() {//每个函数里面都有this 环境对象 普通函数里面this指向的是windowconsole.log(this)}window.fn()</script>
<script>const btn=document.querySelector('button')btn.addEventListener('click',function(){// 事件监听 this指向调用者console.log(this)// btn.style.color='red'this.style.color='red'})</script>5、回调函数
6、案例：Tab栏切换
<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8"><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('.tab-nav a') //console.log(as) 返回数组for (let i = 0; i < as.length; i++) {// 绑定鼠标经过事件as[i].addEventListener('mouseenter', function () {document.querySelector('.tab-nav .active').classList.remove('active')this.classList.add('active')// 图片更换document.querySelector('.tab-content .active').classList.remove('active')document.querySelector(`.tab-content .item:nth-child(${i + 1})`).classList.add('active')})}</script>
</body></html>