思维导图
一、事件监听(绑定)
1.1 事件监听
<!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> </head> <body> <button>点击</button> <script> // 需求: 点击了按钮,弹出一个对话框 // 1. 事件源 按钮 // 2.事件类型 点击鼠标 click 字符串 // 3. 事件处理程序 弹出对话框 const btn = document.querySelector('button') btn.addEventListener('click', function () { alert('你早呀~') }) </script> </body> </html>
李伟兴 09:31:13 <!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> .box { position: relative; width: 1000px; height: 200px; background-color: pink; margin: 100px auto; text-align: center; font-size: 50px; line-height: 200px; font-weight: 700; } .box1 { position: absolute; right: 20px; top: 10px; width: 20px; height: 20px; background-color: skyblue; text-align: center; line-height: 20px; font-size: 16px; cursor: pointer; } </style> </head> <body> <div class="box"> 我是广告 <div class="box1">X</div> </div> <script> // 1. 获取事件源 const box1 = document.querySelector('.box1') // 关闭的是大盒子 const box = document.querySelector('.box') // 2. 事件侦听 box1.addEventListener('click', function () { box.style.display = 'none' }) </script> </body> </html>
解惑:
js垃圾回收机制,函数执行完后,声明的变量回收,下次执行时再创建新的。
<!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> </head> <body> <button>点击</button> <script> const btn = document.querySelector('button') btn.addEventListener('click', function () { const num = Math.random() console.log(num) }) </script> </body> </html>
1.2 拓展阅读-事件监听版本
二、事件类型
<!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"><</button> <button class="next">></button> </div> </div> </div> <script> // 1. 初始数据 const data = [ { 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)' }, ] // 获取元素 const img = document.querySelector('.slider-wrapper img') const p = document.querySelector('.slider-footer p') const footer = document.querySelector('.slider-footer') // 1. 右按钮业务 // 1.1 获取右侧按钮 const next = document.querySelector('.next') let i = 0 // 信号量 控制播放图片张数 // 1.2 注册点击事件 next.addEventListener('click', function () { // console.log(11) i++ // 1.6判断条件 如果大于8 就复原为 0 // if (i >= 8) { // i = 0 // } i = i >= data.length ? 0 : i // 1.3 得到对应的对象 // console.log(data[i]) // 调用函数 toggle() }) // 2. 左侧按钮业务 // 2.1 获取左侧按钮 const prev = document.querySelector('.prev') // 1.2 注册点击事件 prev.addEventListener('click', function () { i-- // 判断条件 如果小于0 则爬到最后一张图片索引号是 7 // if (i < 0) { // i = 7 // } i = i < 0 ? data.length - 1 : i // 1.3 得到对应的对象 // console.log(data[i]) // 调用函数 toggle() }) // 声明一个渲染的函数作为复用 function toggle() { // 1.4 渲染对应的数据 img.src = data[i].url p.innerHTML = data[i].title footer.style.backgroundColor = data[i].color // 1.5 更换小圆点 先移除原来的类名, 当前li再添加 这个 类名 document.querySelector('.slider-indicator .active').classList.remove('active') document.querySelector(`.slider-indicator li:nth-child(${i + 1})`).classList.add('active') } // 3. 自动播放模块 let timerId = setInterval(function () { // 利用js自动调用点击事件 click() 一定加小括号调用函数 next.click() }, 1000) // 4. 鼠标经过大盒子,停止定时器 const slider = document.querySelector('.slider') // 注册事件 slider.addEventListener('mouseenter', function () { // 停止定时器 clearInterval(timerId) }) // 5. 鼠标离开大盒子,开启定时器 // 注册事件 slider.addEventListener('mouseleave', function () { // 停止定时器 if (timerId) clearInterval(timerId) // 开启定时器 timerId = setInterval(function () { // 利用js自动调用点击事件 click() 一定加小括号调用函数 next.click() }, 1000) }) </script> </body> </html>
<!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> </head> <body> <input type="text"> <script> const input = document.querySelector('input') input.addEventListener('focus', function () { console.log('有焦点触发') }) input.addEventListener('blur', function () { console.log('失去焦点触发') }) </script> </body> </html>
键盘事件
<!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> </head> <body> <input type="text"> <script> const input = document.querySelector('input') // 1. 键盘事件 // input.addEventListener('keydown', function () { // console.log('键盘按下了') // }) // input.addEventListener('keyup', function () { // console.log('键盘谈起了') // }) // 2. 用户输入文本事件 input input.addEventListener('input', function () { console.log(input.value) }) </script> </body> </html>
focus伪类选择器也可以监听获得焦点事件,但我们需要更改元素内容,使用JS
<!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> input { width: 200px; transition: all .3s; } /* focus伪类选择器 获得焦点 */ input:focus { width: 300px; } </style> </head> <body> <input type="text"> </body> </html>
三、事件对象
3.1 获取事件对象
<!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> </head> <body> <!-- <button>点击</button> --> <input type="text"> <script> // const btn = document.querySelector('button') // btn.addEventListener('click', function (e) { // console.log(e) // }) const input = document.querySelector('input') input.addEventListener('keyup', function (e) { // console.log(11) // console.log(e.key) if (e.key === 'Enter') { console.log('我按下了回车键') } }) </script> </body> </html>
点击按钮后控制台打印对象:
3.2 事件对象常用属性
<!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> </head> <body> <!-- <button>点击</button> --> <input type="text"> <script> // const btn = document.querySelector('button') // btn.addEventListener('click', function (e) { // console.log(e) // }) const input = document.querySelector('input') input.addEventListener('keyup', function (e) { // console.log(11) // console.log(e.key) if (e.key === 'Enter') { console.log('我按下了回车键') } }) </script> </body> </html>
去字符串左右空格:trim()
<!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> </head> <body> <textarea name="" id="" cols="30" rows="10"></textarea> <script> const str = ' im a teacher ' // console.log(str.trim()) // 去除字符串左右的空格 const tx = document.querySelector('textarea') tx.addEventListener('keyup', function (e) { // console.log(tx.value) if (e.key === 'Enter') { // console.log(tx.value) console.log(tx.value.trim() === '') } }) </script> </body> </html>
<!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 item = document.querySelector('.item') const text = document.querySelector('.text') // 1. 当我们文本域获得了焦点,就让 total 显示出来 tx.addEventListener('focus', function () { total.style.opacity = 1 }) // 2. 当我们文本域失去了焦点,就让 total 隐藏出来 tx.addEventListener('blur', function () { total.style.opacity = 0 }) // 3. 检测用户输入 tx.addEventListener('input', function () { // console.log(tx.value.length) 得到输入的长度 total.innerHTML = `${tx.value.length}/200字` }) // 4. 按下回车发布评论 tx.addEventListener('keyup', function (e) { // 只有按下的是回车键,才会触发 // console.log(e.key) if (e.key === 'Enter') { // 如果用户输入的不为空就显示和打印 if (tx.value.trim()) { // console.log(11) item.style.display = 'block' // console.log(tx.value) // 用户输入的内容 text.innerHTML = tx.value } // 等我们按下回车,结束,清空文本域 tx.value = '' // 按下回车之后,就要把 字符统计 复原 total.innerHTML = '0/200字' } }) </script> </body> </html>
四、 环境对象
五、 回调函数
为什么不使用hover,而要使用鼠标经过事件?
鼠标离开后,元素仍处于active状态
<!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> // 1. a 模块制作 要给 5个链接绑定鼠标经过事件 // 1.1 获取 a 元素 const as = document.querySelectorAll('.tab-nav a') // console.log(as) for (let i = 0; i < as.length; i++) { // console.log(as[i]) // 要给 5个链接绑定鼠标经过事件 as[i].addEventListener('mouseenter', function () { // console.log('鼠标经过') // 排他思想 // 干掉别人 移除类active document.querySelector('.tab-nav .active').classList.remove('active') // 我登基 我添加类 active this 当前的那个 a this.classList.add('active') // 下面5个大盒子 一一对应 .item // 干掉别人 document.querySelector('.tab-content .active').classList.remove('active') // 对应序号的那个 item 显示 添加 active 类 document.querySelector(`.tab-content .item:nth-child(${i + 1})`).classList.add('active') }) } </script> </body> </html>