Pseudo-Class ": Before", ": after" and pseudo-elements ":: Before", ":: After"-css generated content

inserting content into the web, in the CSS2.1 era, relies on javascript for implementation. But after entering the CSS3 we can achieve by CSS3 pseudo-class ": Before", ": After" and CSS3 pseudo-element ":: Before", ":: After", the key is to rely on the "content" property in CSS3. This property, however, does not work for the img and input elements.

Content with CSS pseudo-class or pseudo-elements, generally can do the following four things:

function	function Description
None	Do not generate any content
attr	Insert Tag Property value
Url	Inserts an external resource (image, audio, video, or any other resource supported by the browser) using the specified absolute or relative address
String	Insert String

examples Show:

There is a way to clear the float in CSS called "Clearfix". This "Clearfix" method uses "content", but only inserts a space here. As shown below:

. Clearfix:before,

. clearfix:after {

       content: "";

       display:table;

}

. clearfix:after {

       clear:both;

       Overflow:hidden;

}

The above example is the most common and simplest, and let's look at a method for inserting element property values.

Suppose we have an element:

<a href= "# #" title= "I'm a Title property value, I'm stuck in your back" > I'm the element </a>

You can insert the "title" value of an element into the element's content after I am an element by using ": After" and "Content:attr (title)":

A:after {

  content:attr (title);

       Color: #f00;

}

The effect is as follows: