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 
这是h1
 
这是h2
 #css h1::after{ content:"h1后插入内容" } h2::after{ content:none }

Running results: https://jsfiddle.net/dwqs/ Lmm1r08x/

Embedded text symbols

You can use the open-quote attribute value and close-quote attribute value of the content attribute to add embedded characters such as brackets, single quotes, and double quotes on both sides of the string. Set of text symbols. 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; }

Running result: https://jsfiddle.net/dwqs/p8e3qvv4/

Insert image

The content attribute can also be placed directly in front of the element/ After inserting the picture

#html 
这是h3
 #css h3::after{ content:url(http://ido321.qiniudn.com/wp-content/themes/yusi1.0/img/new.gif) }

Run result: https://jsfiddle.net/dwqs/c6qk6pkv/

Insert the attribute value of the element

The content attribute can directly use attr to obtain the element attribute and insert it into the corresponding position.

#html 这是链接 #css a:after{ content:attr(href); }

Run results: https://jsfiddle.net/dwqs/m220nzan/

Insert item number

Use the counter attribute of content to append consecutive numbers to multiple items.

#html 
大标题
 
文字
 
大标题
 
文字
 
大标题
 
文字
 
大标题
 
文字
 #css h1:before{ content:counter(my)'.'; } h1{ counter-increment:my; }

Running results: https://jsfiddle.net/dwqs/2ueLg3uj/

Project number modification

The default inserted project number is numeric, 1,2 ,3. . . Automatic increment, you can also add text and styles to the project number, still use the above html, css modification is as follows:

h1:before{ content:'第'counter(my)'章'; color:red; font-size:42px; } h1{ counter-increment:my; }

Running results: https://jsfiddle.net/dwqs/17hqznca/

Specify the numbering type

Use the content (counter name, numbering type) format syntax to specify 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; }

Running results: https://jsfiddle.net/dwqs/4nsrtxup/

Number nesting

Large number nesting The numbers are nested within the medium numbers, and the small numbers are nested within the medium numbers.

#html 
大标题
 
文字1
 
文字2
 
文字3
 
大标题
 
文字1
 
文字2
 
文字3
 
大标题
 
文字1
 
文字2
 
文字3
 #css h1::before{ content:counter(h)'.'; } h1{ counter-increment:h; } p::before{ content:counter(p)'.'; margin-left:40px; } p{ counter-increment:p; }

Running results: https://jsfiddle.net/dwqs/2k5qbz51/

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 and modify the css of the above h1:

h1{ counter-increment:h; counter-reset:p; }

In this way, the numbering will be reset. Take a look at the result: https: //jsfiddle.net/dwqs/hfutu4Lq/

You can also achieve more complex nesting, such as three levels of nesting.

#html 
大标题
 
中标题
 
小标题
 
小标题
 
中标题
 
小标题
 
小标题
 
大标题
 
中标题
 
小标题
 
小标题
 
中标题
 
小标题
 
小标题
 #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; }

Run results: https://jsfiddle.net/dwqs/wuuckquy/

Zhang Dada has an article about using counter to implement counting: small tip: CSS counter + pseudo class to achieve numerical dynamics Calculation and presentation

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