What are pseudo elements

Pseudo elements are a powerful selector in CSS that can add extra content to and style specific parts of an element. Two common ways of using it are: 1. ::before, used to insert additional content before the content of the element; 2. ::after, used to insert additional content after the content of the element.

The operating system for this tutorial: Windows 10 system, DELL G3 computer.

Pseudo-element (pseudo-element) is a special selector in CSS that is used to add styles to specific parts of an element without adding additional markup in HTML. The syntax of pseudo-elements is represented by double colons (::), such as ::before and ::after.

The purpose of pseudo-elements is to allow developers to insert additional content before or after the content of the element and to style it. This extra content can be text, images, or any other HTML element. The content of pseudo-elements is generated by CSS rather than taken directly from HTML.

Pseudo elements are commonly used in two ways: ::before and ::after. Among them, ::before is used to insert additional content before the content of the element, and ::after is used to insert additional content after the content of the element. These additional contents can be used to achieve some special effects, such as adding icons, decorative elements, etc.

The use of pseudo-elements is very flexible, and its style can be controlled through CSS properties and values. Attributes that can use pseudo elements include content, display, position, width, height, background, border, etc. By setting the values ​​of these properties, various effects can be achieved.

For example, you can use the pseudo-elements ::before and ::after to create a simple decorative effect. First, you can insert empty content into the pseudo-element by setting the value of the content attribute to double quotes ("") or single quotes (''). Then, you can display the pseudo-element as a block-level element by setting the value of the display attribute to block. Finally, you can set the position of a pseudo-element to an absolute position relative to its parent element by setting the value of the position attribute to absolute. By setting the values ​​of attributes such as width, height, and background, pseudo elements can be styled to achieve different decorative effects.

In addition to ::before and ::after, CSS also provides some other pseudo-elements, such as ::first-line and ::first-letter. ::first-line is used to select the first line of text of an element, while ::first-letter is used to select the first letter of an element. These pseudo-elements can be used to set special styles for text, such as changing fonts, font sizes, colors, etc.

In short, pseudo-elements are a powerful selector in CSS that can add extra content to and style specific parts of an element. Through the flexible use of pseudo elements, various effects can be achieved, thereby improving the visual effects and user experience of the web page. .

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