晋中网站建设百度营业执照怎么办理
事件监听
事件监听版本
事件类型
事件
概念
事件在编程时系统内发生的动作或者发生的事情
例子
点击按钮
鼠标经过
拖拽鼠标
事件监听（注册事件，绑定事件）
让程序员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
语法
元素.addEventListener('事件',要执行的函数)事件监听三要素
事件源：哪个DOM元素被事件触发了，要获取DOM元素
事 件：用什么方式触发，比如:鼠标单击click，鼠标经过mouseover
事件调用什么函数：要做什么
代码
<button>点击我</button><div>经过我</div><script>//1获取按钮元素let btn = document.querySelector("button")//2事件源btn.addEventListener("click", function () {alert("努力学习啊啊啊啊啊啊啊啊")})let box=document.querySelector('div')box.addEventListener("mouseover", function () {alert("努力挣钱啊啊啊啊啊啊啊啊")})</script>例子 关闭二维码
二维码旁边有一个关闭按钮，点击然后关闭二维码
<style>* {margin: 0;padding: 0;}.erweima {position: relative;width: 160px;height: 160px;margin: 100px auto;border: 1px solid #ccc;}.erweima i {position: absolute;left: -13px;top: 0;width: 10px;height: 10px;border: 1px solid #ccc;font-size: 12px;line-height: 10px;color: #ccc;font-style: normal;cursor: pointer;}</style></head><body><div class="erweima"><img src="./images/code.png" alt="" /><i class="close_btn">x</i></div><script>//1获取元素let btn = document.querySelector(".close_btn")let code = document.querySelector(".erweima")//2事件监听btn.addEventListener("click", function () {code.style.display = "none"})</script></body>
例子 随机点名
<style>div {width: 200px;height: 40px;border: 2px solid brown;text-align: center;line-height: 40px;}button {margin-left: 65px;}</style></head><body><div></div><button>click this</button><script>let box = document.querySelector("div")let btn = document.querySelector("button")function getRandom(min, max) {return Math.floor(Math.random() * (max - min + 1)) + min}let arr = ["张三", "李四", "王五", "王朝", "马汉"]btn.addEventListener('click', function () {let random = getRandom(0, arr.length - 1)box.innerHTML = arr[random]})</script></body>
例子 随机点名完善
<style>div {width: 200px;height: 40px;border: 5px solid brown;text-align: center;line-height: 40px;}button {margin-left: 65px;}</style></head><body><div>点击下面按钮开始抽人</div><button>click this</button><script>let box = document.querySelector("div")let btn = document.querySelector("button")function getRandom(min, max) {return Math.floor(Math.random() * (max - min + 1)) + min}let arr = ["张三", "李四", "王五", "王朝", "马汉"]btn.addEventListener("click", function () {let random = getRandom(0, arr.length - 1)box.innerHTML = arr[random]//抽过的就删除arr.splice(random, 1)//抽完按钮就禁用，数组最后一个就禁用if (arr.length === 0) {btn.disabled = truebtn.innerHTML='所有人都已经抽过了'}})</script></body>事件类型
鼠标事件
鼠标触发
click 鼠标点击
mouseover鼠标经过
mouseleave鼠标离开
焦点事件
表单获得光标
focus获得焦点
blur失去焦点
键盘事件
键盘触发
KeyDown键盘按下触发
keyup键盘抬起触发
文本事件
表单输入触发
input用户输入事件
例子 小米搜索框
<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: 5px 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>//1获取元素inputlet search = document.querySelector("input")//2获取元素.result-listlet list = document.querySelector(".result-list")//3事件监听，获得光标事件search.addEventListener("focus", function () {//显示下拉菜单list.style.display = "block"//文本框变色search.classList.add("search")})</script></body>
例子 输入文字，计算用户输入的字数
<body><div class="w"><div class="controls"><img src="images/tip.png" alt="" /><br /><textareaplaceholder="说点什么吧..."id="area"cols="30"rows="10"maxlength="200"></textarea><div><span class="useCount">0</span><span>/</span><span>200</span><button id="send">发布</button></div></div><div class="contentList"><ul></ul></div></div><script>//1获取元素文本域arealet area = document.querySelector("#area")//2获取字符长度usecountlet useCount = document.querySelector(".useCount")//3监听绑定事件，用户输入的inputarea.addEventListener("input", function () {useCount.innerHTML = area.value.length})</script></body>
例子 全选文本
<style>* {margin: 0;padding: 0;}table {border-collapse: collapse;border-spacing: 0;border: 1px solid #c0c0c0;width: 500px;margin: 100px auto;text-align: center;}th {background-color: #09c;font: bold 16px "微软雅黑";color: #fff;height: 24px;}td {border: 1px solid #d0d0d0;color: #404060;padding: 10px;}.allCheck {width: 80px;}</style></head><body><table><tr><th class="allCheck"><input type="checkbox" name="" id="checkAll" /><span class="all">全选</span></th><th>商品</th><th>商家</th><th>价格</th></tr><tr><td><input type="checkbox" name="check" class="ck" /></td><td>小米手机</td><td>小米</td><td>￥1999</td></tr><tr><td><input type="checkbox" name="check" class="ck" /></td><td>小米净水器</td><td>小米</td><td>￥4999</td></tr><tr><td><input type="checkbox" name="check" class="ck" /></td><td>小米电视</td><td>小米</td><td>￥5999</td></tr></table><script>//let all = document.querySelector("#checkAll")//let cks = document.querySelectorAll(".ck")//let span = document.querySelector("span")//点全选按钮，下面的小按钮都选上all.addEventListener("click", function () {for (let i = 0; i < cks.length; i++) {cks[i].checked = all.checked}//如果点击全选了，全选文字就变成取消，没有点击就是全选if (all.checked === true) {span.innerHTML = "取消"} else {span.innerHTML = "全选"}})//点击下面小按钮，全选按钮被选for (let i = 0; i < cks.length; i++) {cks[i].addEventListener("click", function () {for (let j = 0; j < cks.length; j++) {if (cks[j].checked === false) {all.checked === falsereturn}}//all.checked = true})}</script></body>
例子 购物车加减操作
<style>div {width: 80px;}input[type=text] {width: 50px;height: 44px;outline: none;border: 1px solid #ccc;text-align: center;border-right: 0;}input[type=button] {height: 24px;width: 22px;cursor: pointer;}input {float: left;border: 1px solid #ccc;}</style>
</head><body><div><input type="text" id="total" value="1" readonly><input type="button" value="+" id="add"><input type="button" value="-" id="reduce" disabled><script>// 1. 获取元素 三个let total = document.querySelector('#total')let add = document.querySelector('#add')let reduce = document.querySelector('#reduce')// 2. 点击加号 事件侦听 add.addEventListener('click', function () {// console.log(typeof total.value)// total.value = total.value + 1// i++ 隐式转换// i = i + 1 total.value++reduce.disabled = false})// 3. 点击减号 事件侦听 reduce.addEventListener('click', function () {total.value--if (total.value <= 1) {reduce.disabled = true}})</script></div>
</body