1、页面加载事件
加载外部资源（如图片、外联CSS和JavaScript等）加载完毕时触发的事件
为什么要学？
- 有些时候需要等页面资源全部处理完了做一些事情
- 老代码喜欢把script写head中，这时候直接找dom元素找不到
事件名：load
监听页面所有资源加载完毕：
- 给window添加load事件
注意：不光可以监听整个页面资源加载完毕，也可以针对某个资源绑定load事件
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<script>
// 等待页面所有资源加载完毕，就会去执行回调函数
window.addEventListener('load',function(){
const btn = document.querySelector('button')
btn.addEventListener('click',function(){
alert(11)
})
})
// img.addEventListener('load',function(){
// 等待图片加载完毕，再去执行里面的代码
// })
</script>
</head>
<body>
<button>点击</button>
</body>
</html>当初始的HTML文档被完全加载和解析完成之后，DOMContentLoaded事件被触发，而无需等待样式表、图像等完全加载
事件名：DOMContentLoaded
监听页面DOM加载完毕
- 给document添加DOMContentLoaded事件
document.addEventListener('DOMContentLoaded', function(){
const btn = document.querySelector('button')
btn.addEventListener('click',function(){
alert(11)
})
})2、元素滚动事件
滚动条在滚动的时候持续触发的事件
为什么要学？
- 很多网页需要检测用户把页面滚动到某个区域后做一些处理，比如固定导航栏，返回顶部
事件名：scroll
监听整个页面滚动
- 给window或document添加scroll事件
监听某个元素的内部滚动直接给某个元素添加即可
<script>
// 页面滚动事件
window.addEventListener('scroll',function () {
// 执行的操作
console.log('我滚了');
})
</script>2.1 scrollLeft和scrollTop（属性）
scrollLeft和scrollTop（属性）：
- 获取被卷去的大小
- 获取元素内容往左、往上滚出去看不到的距离
- 这两个值是可读写的
尽量在scroll事件里面获取被卷去的距离
<!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>
body {
padding-top: 100px;
height: 3000px;
}
div {
display: none;
margin: 100px;
overflow: scroll;
width: 200px;
height: 200px;
border: 1px solid #000;
}
</style>
</head>
<body>
<div>
我好饿好饿好饿好饿好饿好
今天去吃什么吃什么吃什么
早上吃什么吃什么吃什么什
中午吃什么吃什么吃什么什
晚上吃什么吃什么吃什么什
第二天吃什么吃什么吃什么
明天去那玩去哪玩去哪玩去
你去哪找工作啊找工作找工
带带我呗带带我带带我哪玩
你啥时候一夜暴富暴富暴富
减肥十斤减肥减肥哪玩哪玩
减肥五斤瘦成闪电闪电哪玩
减肥两斤减肥减肥哪玩哪玩
算了，还是吃饱在减哪玩哪
明天去跑去去跑步去跑去牙
早上，这么早，在睡会吧吧
中午：都中午了，就不跑了
晚上：天好黑啊，还是明天
</div>
<script>
const div = document.querySelector('div')
// 页面滚动事件
window.addEventListener('scroll',function () {
// console.log('我滚了');
// // 我想知道页面到底滚动了多少像素，被卷去了多少 scrollTop
// 获取html元素写法
// document.documentElement
// console.log(document.documentElement.scrollTop)
const n = document.documentElement.scrollTop
if(n >= 100){
div.style.display = 'block'
}else{
div.style.display = 'none'
}
})
// const div = document.querySelector('div')
// div.addEventListener('scroll',function (){
// // console.log(111)
// // scrollTop 被卷去的头部
// console.log(div.scrollTop)
// })
</script>
</body>
</html>2.2 页面滚动事件-获取位置
开发中，经常会检测页面滚动的距离，比如页面滚动100像素，就可以显示一个元素，或者固定一个元素
注意事项：document.documentElement HTML文档返回对象为HTML元素
2.3 练习电梯导航案例
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>小兔鲜儿 - 新鲜 惠民 快捷!</title>
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="renderer" content="webkit">
<link rel="stylesheet" href="./css/common.css">
<link rel="stylesheet" href="./css/index.css">
</head>
<body>
<!-- 项部导航 -->
<div class="xtx_topnav">
<div class="wrapper">
<!-- 顶部导航 -->
<ul class="xtx_navs">
<li>
<a href="javascript:;">请先登录</a>
</li>
<li>
<a href="javascript:;">免费注册</a>
</li>
<li>
<a href="javascript:;">我的订单</a>
</li>
<li>
<a href="javascript:;">会员中心</a>
</li>
<li>
<a href="javascript:;">帮助中心</a>
</li>
<li>
<a href="javascript:;">在线客服</a>
</li>
<li>
<a href="javascript:;">
<i class="mobile sprites"></i>
手机版
</a>
</li>
</ul>
</div>
</div>
<!-- 头部 -->
<div class="xtx_header">
<div class="wrapper">
<!-- 网站Logo -->
<h1 class="xtx_logo"><a href="/">小兔鲜儿</a></h1>
<!-- 主导航 -->
<div class="xtx_navs">
<ul class="clearfix">
<li>
<a href="javascript:;">首页</a>
</li>
<li>
<a href="javascript:;">生鲜</a>
</li>
<li>
<a href="javascript:;">美食</a>
</li>
<li>
<a href="javascript:;">餐厨</a>
</li>
<li>
<a href="javascript:;">电器</a>
</li>
<li>
<a href="javascript:;">居家</a>
</li>
<li>
<a href="javascript:;">洗护</a>
</li>
<li>
<a href="javascript:;">孕婴</a>
</li>
<li>
<a href="javascript:;">服装</a>
</li>
</ul>
</div>
<!-- 站内搜索 -->
<div class="xtx_search clearfix">
<!-- 购物车 -->
<a href="javascript:;" class="xtx_search_cart sprites">
<i>2</i>
</a>
<!-- 搜索框 -->
<div class="xtx_search_wrapper">
<input type="text" placeholder="搜一搜">
</div>
</div>
</div>
</div>
<!-- 分类及焦点图 -->
<div class="xtx_entry">
<div class="wrapper">
<!-- 分类 -->
<div class="xtx_category">
<!-- 顶级分类 -->
<ul class="xtx_category_super">
<li>
<a href="javascript:;">
生鲜
<small>水果</small>
<small>蔬菜</small>
</a>
<i class="sprites"></i>
</li>
<li class="active">
<a href="javascript:;">
美食
<small>面点</small>
<small>干果</small>
</a>
<i class="sprites"></i>
</li>
<li>
<a href="javascript:;">
电器
<small>数码产品</small>
</a>
<i class="sprites"></i>
</li>
<li>
<a href="javascript:;">
居家
<small>床品</small>
<small>四件套</small>
<small>被枕</small>
</a>
<i class="sprites"></i>
</li>
<li>
<a href="javascript:;">
洗护
<small>洗发洗护</small>
<small>美妆</small>
</a>
<i class="sprites"></i>
</li>
<li>
<a href="javascript:;">
孕婴
<small>奶粉</small>
<small>玩具</small>
<small>辅食</small>
</a>
<i class="sprites"></i>
</li>
<li>
<a href="javascript:;">
餐橱
<small>数码产品</small>
</a>
<i class="sprites"></i>
</li>
<li>
<a href="javascript:;">
服饰
<small>女装</small>
<small>男装</small>
</a>
<i class="sprites"></i>
</li>
<li>
<a href="javascript:;">
杂货
<small>户外</small>
<small>图书</small>
</a>
<i class="sprites"></i>
</li>
<li>
<a href="javascript:;">
品牌
<small>品牌制造</small>
</a>
<i class="sprites"></i>
</li>
</ul>
<!-- 子分类 -->
<div class="xtx_category_subset">
</div>
</div>
<!-- 焦点图 -->
<div class="xtx_banner">
<ul>
<li>
<a href="javascript:;">
<img src="./uploads/banner_1.png" alt="">
</a>
</li>
</ul>
<!-- 切换按钮 -->
<a href="javascript:;" class="prev sprites"></a>
<a href="javascript:;" class="next sprites"></a>
<!-- 指示器 -->
<div class="indicator">
<span></span>
<span></span>
<span class="active"></span>
<span></span>
<span></span>
</div>
</div>
</div>
</div>
<!-- 新鲜好物 -->
<div class="xtx_goods_new xtx_panel">
<div class="wrapper">
<!-- 面板头部 -->
<div class="xtx_panel_header">
<h3>新鲜好物<small>新鲜出炉 品质靠谱</small></h3>
<a href="javascript:;" class="more">
查看全部<i class="sprites"></i>
</a>
</div>
<!-- 商品列表 -->
<div class="xtx_panel_goods_1">
<a href="javascript:;">
<img src="./uploads/new_goods_1.jpg" alt="">
<span class="name">睿米无线吸尘器F8</span>
<span class="price"><small>￥</small>899</span>
</a>
<a href="javascript:;">
<img src="./uploads/new_goods_2.jpg" alt="">
<span class="name">智能环绕3D空调</span>
<span class="price"><small>￥</small>1299</span>
</a>
<a href="javascript:;">
<img src="./uploads/new_goods_3.jpg" alt="">
<span class="name">广东软软糯米煲仔饭</span>
<span class="price"><small>￥</small>129</span>
</a>
<a href="javascript:;">
<img src="./uploads/new_goods_4.jpg" alt="">
<span class="name">罗西机械智能手表</span>
<span class="price"><small>￥</small>3399</span>
</a>
</div>
</div>
</div>
<!-- 人气推荐 -->
<div class="xtx_goods_popular xtx_panel">
<div class="wrapper">
<!-- 面板头部 -->
<div class="xtx_panel_header">
<h3>人气推荐<small>人气爆款 不容错过</small></h3>
</div>
<!-- 商品列表 -->
<div class="xtx_panel_goods_1">
<a href="javascript:;">
<img src="./uploads/popular_1.jpg">
<span class="title">特惠推荐</span>
<span class="alt">我猜得到 你的需要</span>
</a>
<a href="./index-hot.html">
<img src="./uploads/popular_2.jpg">
<span class="title">爆款推荐</span>
<span class="alt">人气好物推荐</span>
</a>
<a href="./index-one.html">
<img src="./uploads/popular_3.jpg">
<span class="title">场景使用一站买全</span>
<span class="alt">编辑精心整理推荐</span>
</a>
<a href="javascript:;">
<img src="./uploads/popular_4.jpg">
<span class="title">领券中心</span>
<span class="alt">发现更多超值优惠券</span>
</a>
</div>
</div>
</div>
<!-- 热门品牌 -->
<div class="xtx_goods_brand xtx_panel">
<div class="wrapper">
<div class="xtx_panel_header">
<h3>热门品牌<small>国际经典 品质保证</small></h3>
<div class="page-bar">
<a href="javascript:;" class="prev sprites"></a>
<a href="javascript:;" class="next sprites active"></a>
</div>
</div>
<!-- 商品列表 -->
<div class="xtx_goods">
<ul>
<li>
<a href="./index-brand.html">
<img src="./uploads/brand_goods_1.jpg" alt="">
</a>
<a href="./brand-list.html">
<img src="./uploads/brand_goods_2.jpg" alt="">
</a>
<a href="javascript:;">
<img src="./uploads/brand_goods_3.jpg" alt="">
</a>
<a href="javascript:;">
<img src="./uploads/brand_goods_4.jpg" alt="">
</a>
<a href="javascript:;">
<img src="./uploads/brand_goods_5.jpg" alt="">
</a>
</li>
</ul>
</div>
</div>
</div>
<!-- 分类商品 -->
<div class="xtx_goods_category xtx_panel">
<div class="wrapper">
<!-- 生鲜 -->
<div class="xtx_panel_header">
<h3>生鲜</h3>
<a href="javascript:;" class="more">
查看全部<i class="sprites"></i>
</a>
<div class="tabs-bar">
<a href="javascript:;" class="active">水果</a>
<a href="javascript:;">蔬菜</a>
<a href="javascript:;">肉禽蛋</a>
<a href="javascript:;">裤装</a>
<a href="javascript:;">衬衫</a>
<a href="javascript:;">内衣</a>
</div>
</div>
<!-- 商品列表 -->
<div class="xtx_panel_goods_2">
<ul class="clearfix">
<li>
<a href="javascript:;">
<img src="./uploads/fresh_goods_cover.jpg" alt="">
</a>
<div class="label">
<span>生鲜馆</span>
<span>全场3件8折</span>
</div>
</li>
<li>
<!-- 商品图片 -->
<a href="javascript:;">
<div class="img-box">
<img src="./uploads/fresh_goods_1.jpg" alt="">
</div>
</a>
<!-- 商品信息 -->
<div class="meta">
<p class="name">美威 智利原味三文鱼排 240g/袋 4片装</p>
<p class="flag">海鲜年货</p>
<p class="price"><small>￥</small>59</p>
</div>
<!-- 其它 -->
<div class="extra">
<a href="javascript:;">
<span>找相似</span>
<span>发现现多宝贝></span>
</a>
</div>
</li>
<li>
<a href="javascript:;">
<div class="img-box">
<img src="./uploads/fresh_goods_2.jpg" alt="">
</div>
</a>
<div class="meta">
<p class="name">红功夫 麻辣小龙虾1.5kg 4-6钱/25-32只</p>
<p class="flag">火锅食材</p>
<p class="price"><small>￥</small>71.9</p>
</div>
<!-- 其它 -->
<div class="extra">
<a href="javascript:;">
<span>找相似</span>
<span>发现现多宝贝></span>
</a>
</div>
</li>
<li>
<a href="javascript:;">
<div class="img-box">
<img src="./uploads/fresh_goods_3.jpg" alt="">
</div>
</a>
<div class="meta">
<p class="name">三都港 冷冻无公害黄花鱼 700g 2条 袋装</p>
<p class="flag">海鲜水产</p>
<p class="price"><small>￥</small>49.9</p>
</div>
<!-- 其它 -->
<div class="extra">
<a href="javascript:;">
<span>找相似</span>
<span>发现现多宝贝></span>
</a>
</div>
</li>
<li>
<a href="javascript:;">
<div class="img-box">
<img src="./uploads/fresh_goods_4.jpg" alt="">
</div>
</a>
<div class="meta">
<p class="name">渔公码头 大连鲜食入味 即食海参 辽参刺参 调味海</p>
<p class="flag">海鲜年货</p>
<p class="price"><small>￥</small>899</p>
</div>
<!-- 其它 -->
<div class="extra">
<a href="javascript:;">
<span>找相似</span>
<span>发现现多宝贝></span>
</a>
</div>
</li>
<li>
<a href="javascript:;">
<div class="img-box">
<img src="./uploads/fresh_goods_5.jpg" alt="">
</div>
</a>
<div class="meta">
<p class="name">越南进口白心火龙果4个 装 标准果 单果400-550g </p>
<p class="flag"></p>
<p class="price"><small>￥</small>29</p>
</div>
<!-- 其它 -->
<div class="extra">
<a href="javascript:;">
<span>找相似</span>
<span>发现现多宝贝></span>
</a>
</div>
</li>
<li>
<a href="javascript:;">
<div class="img-box">
<img src="./uploads/fresh_goods_6.jpg" alt="">
</div>
</a>
<div class="meta">
<p class="name">广西沃柑 柑橘1.5kg</p>
<p class="flag">新鲜水果</p>
<p class="price"><small>￥</small>59</p>
</div>
<!-- 其它 -->
<div class="extra">
<a href="javascript:;">
<span>找相似</span>
<span>发现现多宝贝></span>
</a>
</div>
</li>
<li>
<a href="javascript:;">
<div class="img-box">
<img src="./uploads/fresh_goods_7.jpg" alt="">
</div>
</a>
<div class="meta">
<p class="name">进口 牛油果 6个装 单果重约130-180g</p>
<p class="flag">新鲜水果</p>
<p class="price"><small>￥</small>39.9</p>
</div>
<!-- 其它 -->
<div class="extra">
<a href="javascript:;">
<span>找相似</span>
<span>发现现多宝贝></span>
</a>
</div>
</li>
<li>
<a href="javascript:;">
<div class="img-box">
<img src="./uploads/fresh_goods_8.jpg" alt="">
</div>
</a>
<div class="meta">
<p class="name">泰国进口山竹5A级 500g </p>
<p class="flag">新鲜水果</p>
<p class="price"><small>￥</small>29.9</p>
</div>
<!-- 其它 -->
<div class="extra">
<a href="javascript:;">
<span>找相似</span>
<span>发现现多宝贝></span>
</a>
</div>
</li>
</ul>
</div>
<!-- 服饰 -->
<div class="xtx_panel_header">
<h3>服饰</h3>
<a href="javascript:;" class="more">
查看全部<i class="sprites"></i>
</a>
<div class="tabs-bar">
<a href="javascript:;" class="active">行李箱</a>
<a href="javascript:;">男士包袋</a>
<a href="javascript:;">女士包袋</a>
<a href="javascript:;">钱包及小提袋</a>
<a href="javascript:;">男鞋</a>
<a href="javascript:;">女鞋</a>
<a href="javascript:;">拖鞋</a>
</div>
</div>
<!-- 商品列表 -->
<div class="xtx_panel_goods_2">
<ul class="clearfix">
<li>
<a href="javascript:;">
<img src="./uploads/clothes_goods_cover.jpg" alt="">
</a>
<div class="label">
<span>服饰馆</span>
<span>3折狂欢</span>
</div>
</li>
<li>
<!-- 商品图片 -->
<a href="javascript:;">
<div class="img-box">
<img src="./uploads/clothes_goods_1.jpg" alt="">
</div>
</a>
<!-- 商品信息 -->
<div class="meta">
<p class="name">人本秋季厚底帆布鞋 韩版低帮增高学生</p>
<p class="flag"></p>
<p class="price"><small>￥</small>55</p>
</div>
<!-- 其它 -->
<div class="extra">
<a href="javascript:;">
<span>找相似</span>
<span>发现现多宝贝></span>
</a>
</div>
</li>
<li>
<a href="javascript:;">
<div class="img-box">
<img src="./uploads/clothes_goods_2.jpg" alt="">
</div>
</a>
<div class="meta">
<p class="name">迪士尼真皮针扣表带宽度 14-16mm规格双色压纹 女表带</p>
<p class="flag">海鲜年货</p>
<p class="price"><small>￥</small>20.9</p>
</div>
<!-- 其它 -->
<div class="extra">
<a href="javascript:;">
<span>找相似</span>
<span>发现现多宝贝></span>
</a>
</div>
</li>
<li>
<a href="javascript:;">
<div class="img-box">
<img src="./uploads/clothes_goods_3.jpg" alt="">
</div>
</a>
<div class="meta">
<p class="name">三都港 冷冻无公害黄花鱼 700g 2条 袋装</p>
<p class="flag">海鲜水产</p>
<p class="price"><small>￥</small>209</p>
</div>
<!-- 其它 -->
<div class="extra">
<a href="javascript:;">
<span>找相似</span>
<span>发现现多宝贝></span>
</a>
</div>
</li>
<li>
<a href="javascript:;">
<div class="img-box">
<img src="./uploads/clothes_goods_4.jpg" alt="">
</div>
</a>
<div class="meta">
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<li>
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</a>
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吃这些美食才不算辜负自己
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<script>
// 获取元素
const elevator = document.querySelector('.xtx-elevator')
// 1. 当前页面滚动大于300像素，就显示 电梯导航
// 2. 给页面添加滚动事件
window.addEventListener('scroll',function () {
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// const n = document.documentElement.scrollTop
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backTop.addEventListener('click',function () {
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windwo.scrollTo(0,0)
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</body>
</html>2.4 页面滚动事件-滚动到指定的坐标（了解）
scrollTo() 方法可以把内容滚动到指定的坐标
语法：元素.scrollTox(x,y)
3、页面尺寸事件
会在窗口尺寸改变的时候触发事件：
- resize
检测屏幕宽度
获取宽度：
- 获取元素的可见部分宽高（不包含边框，margin，滚动条等）
- clientWidth和clientHeight
<!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>
div {
display: inline-block;
width: 200px;
height: 200px;
background-color: burlywood;
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>4、元素尺寸与位置
使用场景：
- 前面案例滚动多少距离，都是我们自己算的，最好是页面滚动到某个元素，就可以做某些事
- 简单说，就是通过js的方式，得到元素在页面中的位置
- 这样我们可以做，页面滚动这个位置，就可以做某些操作，省去计算了
4.1 尺寸
获取宽高
- 获取元素的自身宽高、包含元素自身设置的宽高、padding、border
- offsetWidth和offsetHeight
- 获取出来的是数值，方便计算
- 注意：获取的是可视宽高，如果盒子是隐藏的，获取的结果是0
获取位置
- 获取元素距离自己定位父级元素的左、上距离
- offsetLeft和offsettop 注意是只读属性
<!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>
div {
position: relative;
width: 200px;
height: 200px;
background-color: blueviolet;
margin: 100px;
}
p {
width: 100px;
height: 100px;
background-color: palegreen;
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>获取位置：
element.getBoundingClientRect()
方法返回元素的大小以及其相对于视口的位置
<!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>
body {
height: 2000px;
}
div {
width: 200px;
height: 200px;
background-color: brown;
margin: 100px;
}
</style>
</head>
<body>
<div></div>
<script>
const div = document.querySelector('div')
console.log(div.getBoundingClientRect())
</script>
</body>
</html>总结：
