gpt4 book ai didi

html - 为什么要用伪元素来分隔 block 元素?

转载 作者:行者123 更新时间:2023-11-28 00:55:31 25 4
gpt4 key购买 nike

我的问题是关于 w3school 上关于响应式网格设计的示例。

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
* {
box-sizing: border-box;
}
.row::after {
content: "";
clear: both;
display: table;
}
[class*="col-"] {
float: left;
padding: 15px;
}
html {
font-family: "Lucida Sans", sans-serif;
}
.header {
background-color: #9933cc;
color: #ffffff;
padding: 15px;
}
.menu ul {
list-style-type: none;
margin: 0;
padding: 0;
}
.menu li {
padding: 8px;
margin-bottom: 7px;
background-color: #33b5e5;
color: #ffffff;
box-shadow: 0 1px 3px rgba(0,0,0,0.12), 0 1px 2px rgba(0,0,0,0.24);
}
.menu li:hover {
background-color: #0099cc;
}
.aside {
background-color: #33b5e5;
padding: 15px;
color: #ffffff;
text-align: center;
font-size: 14px;
box-shadow: 0 1px 3px rgba(0,0,0,0.12), 0 1px 2px rgba(0,0,0,0.24);
}
.footer {
background-color: #0099cc;
color: #ffffff;
text-align: center;
font-size: 12px;
padding: 15px;
}
/* For mobile phones: */
[class*="col-"] {
width: 100%;
}
@media only screen and (min-width: 768px) {
/* For desktop: */
.col-1 {width: 8.33%;}
.col-2 {width: 16.66%;}
.col-3 {width: 25%;}
.col-4 {width: 33.33%;}
.col-5 {width: 41.66%;}
.col-6 {width: 50%;}
.col-7 {width: 58.33%;}
.col-8 {width: 66.66%;}
.col-9 {width: 75%;}
.col-10 {width: 83.33%;}
.col-11 {width: 91.66%;}
.col-12 {width: 100%;}
}
</style>
</head>
<body>

<div class="header">
<h1>Chania</h1>
</div>

<div class="row">

<div class="col-3 menu">
<ul>
<li>The Flight</li>
<li>The City</li>
<li>The Island</li>
<li>The Food</li>
</ul>
</div>

<div class="col-6">
<h1>The City</h1>
<p>Chania is the capital of the Chania region on the island of Crete. The city can be divided in two parts, the old town and the modern city.</p>
</div>

<div class="col-3 right">
<div class="aside">
<h2>What?</h2>
<p>Chania is a city on the island of Crete.</p>
<h2>Where?</h2>
<p>Crete is a Greek island in the Mediterranean Sea.</p>
<h2>How?</h2>
<p>You can reach Chania airport from all over Europe.</p>
</div>
</div>

</div>

<div class="footer">
<p>Resize the browser window to see how the content respond to the resizing.</p>
</div>

</body>
</html>

在此示例中,它使用 .row::after 来分隔 rowfooter。如果我去掉 row 的伪元素,footer 的背景将扩展到整行。我想知道这是为什么?据我了解,rowfooter 都是 display:block,它们不应该只是相互堆叠吗?为什么footer的背景不使用伪元素会扩展?

最佳答案

伪元素用于清除包含在.row 中的 float 。它被称为 clearfix

没有clearfix:

.row::after {
content: "";
clear: both;
display: table;
}

.col-md-6 {
float: left;
width: 50%;
}

.row-color {
background-color: gold;
}
<div class="row-color">
<div class="col-md-6">
Left
</div>
<div class="col-md-6">
Right
</div>
</div>

使用 clearfix:

.row::after {
content: "";
clear: both;
display: table;
}

.col-md-6 {
float: left;
width: 50%;
}

.row-color {
background-color: gold;
}
<div class="row row-color">
<div class="col-md-6">
Left
</div>
<div class="col-md-6">
Right
</div>
</div>

关于html - 为什么要用伪元素来分隔 block 元素?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/45172548/

25 4 0
Copyright 2021 - 2024 cfsdn All Rights Reserved 蜀ICP备2022000587号
广告合作:1813099741@qq.com 6ren.com