There are four main pseudo-elements in CSS: before/after/first-letter/first-line. In the before/after pseudo-element selector, there is a content attribute that can insert content into the page.
Insert plain text
content: "Inserted article", or content:none does not insert content
#html
<h1>这是h1</h1>
<h2>这是h2</h2>
#css
h1::after{
content:"h1后插入内容"
}
h2::after{
content:none
}Embedded text symbols
You can use the content attribute The open-quote attribute value and the close-quote attribute value add nested literal symbols such as brackets, single quotes, and double quotes on both sides of the string. open-quote is used to add the starting text symbol, and close-quote is used to add the ending text symbol. Modify the above css:
h1{
quotes:"(" ")"; /*利用元素的quotes属性指定文字符号*/
}
h1::before{
content:open-quote;
}
h1::after{
content:close-quote;
}
h2{
quotes:"\"" "\""; /*添加双引号要转义*/
}
h2::before{
content:open-quote;
}
h2::after{
content:close-quote;
}Insert picture
content attribute can also insert pictures directly before/after the element
#html
<h3>这是h3</h3>
#css
h3::after{
content:url(图片路径)
}Insert attribute value of element
The content attribute can directly use attr to obtain the attributes of the element and insert it into the corresponding position.
#html
<a href="http://www.php.cn">这是链接</a>
#css
a:after{
content:attr(href);
}Insert item number
Use the counter attribute of content to append consecutive numbers to multiple items.
#html
<h1>大标题</h1>
<p>文字</p>
<h1>大标题</h1>
<p>文字</p>
<h1>大标题</h1>
<p>文字</p>
<h1>大标题</h1>
<p>文字</p>
#css
h1:before{
content:counter(my)'.';
}
h1{
counter-increment:my;
}Item number modification
The default inserted item number It is numerical, 1,2,3. . . Automatic increment, you can also add text and styles to the project number. Still use the above html, css modification as follows:
h1:before{
content:'第'counter(my)'章';
color:red;
font-size:42px;
}
h1{
counter-increment:my;
}Specify number type
Use content (counter name, number type) format The syntax specifies the numbering type. The reference to the numbering type can be based on the list-style-type attribute value of ul. Using the above html, the css is modified as follows:
h1:before{
content:counter(my,upper-alpha);
color:red;
font-size:42px;
}
h1{
counter-increment:my;
}Number nesting
Large numbers are nested within medium numbers, and medium numbers are nested within small numbers.
#html
<h1>大标题</h1>
<p>文字1</p>
<p>文字2</p>
<p>文字3</p>
<h1>大标题</h1>
<p>文字1</p>
<p>文字2</p>
<p>文字3</p>
<h1>大标题</h1>
<p>文字1</p>
<p>文字2</p>
<p>文字3</p>
#css
h1::before{
content:counter(h)'.';
}
h1{
counter-increment:h;
}
p::before{
content:counter(p)'.';
margin-left:40px;
}
p{
counter-increment:p;
}It can be found in the output of the example that the numbers of p are consecutive. If you renumber the three p's after each h1, you can use the counter-reset attribute to reset it. Modifying the css of the above h1:
h1{
counter-increment:h;
counter-reset:p;
}can also achieve more complex nesting, such as three-level nesting. .
#html
<h1>大标题</h1>
<h2>中标题</h2>
<h3>小标题</h3>
<h3>小标题</h3>
<h2>中标题</h2>
<h3>小标题</h3>
<h3>小标题</h3>
<h1>大标题</h1>
<h2>中标题</h2>
<h3>小标题</h3>
<h3>小标题</h3>
<h2>中标题</h2>
<h3>小标题</h3>
<h3>小标题</h3>
#css
h1::before{
content:counter(h1)'.';
}
h1{
counter-increment:h1;
counter-reset:h2;
}
h2::before{
content:counter(h1) '-' counter(h2);
}
h2{
counter-increment:h2;
counter-reset:h3;
margin-left:40px;
}
h3::before{
content:counter(h1) '-' counter(h2) '-' counter(h3);
}
h3{
counter-increment:h3;
margin-left:80px;
}The complete DEMO is given below
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>CSS content</title>
<style>
.string p:after {
margin-left: -16px;
background: #fff;
content: "支持";
color: #f00;
}
.attr p:after {
content: attr(title);
}
.url p:before {
content: url(https://img.php.cn/upload/article/000/000/009/587d87ecca52d563.jpg);
display: block;
}
.test ol {
margin: 16px 0;
padding: 0;
list-style: none;
}
.counter1 li {
counter-increment: testname;
}
.counter1 li:before {
content: counter(testname)":";
color: #f00;
font-family: georgia,serif,sans-serif;
}
.counter2 li {
counter-increment: testname2;
}
.counter2 li:before {
content: counter(testname2,lower-roman)":";
color: #f00;
font-family: georgia,serif,sans-serif;
}
.counter3 ol ol {
margin: 0 0 0 28px;
}
.counter3 li {
padding: 2px 0;
counter-increment: testname3;
}
.counter3 li:before {
content: counter(testname3,float)":";
color: #f00;
font-family: georgia,serif,sans-serif;
}
.counter3 li li {
counter-increment: testname4;
}
.counter3 li li:before {
content: counter(testname3,decimal)"."counter(testname4,decimal)":";
}
.counter3 li li li {
counter-increment: testname5;
}
.counter3 li li li:before {
content: counter(testname3,decimal)"."counter(testname4,decimal)"."counter(testname5,decimal)":";
}
</style>
</head>
<body>
<ul>
<li>
<strong>string：</strong>
<p>你的浏览器是否支持content属性：否</p>
</li>
<li>
<strong>attr：</strong>
<p title="如果你看到我则说明你目前使用的浏览器支持content属性"></p>
</li>
<li>
<strong>url()：</strong>
<p>如果你看到图片则说明你目前使用的浏览器支持content属性</p>
</li>
<li>
<strong>counter(name)：</strong>
<ol>
<li>列表项</li>
<li>列表项</li>
<li>列表项</li>
</ol>
</li>
<li>
<strong>counter(name,list-style-type)：</strong>
<ol>
<li>列表项</li>
<li>列表项</li>
<li>列表项</li>
</ol>
</li>
<li>
<strong>counter(name)拓展应用：</strong>
<ol>
<li>列表项
<ol>
<li>列表项
<ol>
<li>列表项</li>
<li>列表项</li>
</ol>
</li>
<li>列表项</li>
</ol>
</li>
<li>列表项
<ol>
<li>列表项</li>
<li>列表项</li>
</ol>
</li>
<li>列表项
<ol>
<li>列表项</li>
<li>列表项</li>
</ol>
</li>
</ol>
</li>
</ul>
</body>
</html>
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
