What are pseudo-classes and pseudo-elements in css

Pseudo-classes in CSS are selectors used to select elements that are in a specific state, which are usually invisible or not represented by the class or ID of the HTML element itself. Pseudo-elements in CSS are more like child elements of an element, but they are not actually part of the real DOM tree. Pseudo-elements allow applying styles to specific parts of an element without adding additional HTML markup. Pseudo-classes and pseudo-elements provide a flexible way to select and style specific elements or element states, and they are very useful tools in CSS.

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

In CSS, pseudo-classes and pseudo-elements are special CSS selectors that can be used to select and style some specific elements or element states.

1. Pseudo-class is a selector used to select elements in a specific state. These states are usually invisible or not represented by the class or ID of the HTML element itself. For example, the :hover pseudo-class can be used to select the element that the mouse pointer is hovering over.

a:hover {  
    color: red;  
}

In this example, when the mouse is hovered over the link ( element), the color of the link will change to red.

In addition to :hover, there are many other pseudo-classes, such as :active (select elements activated by the user), :visited (select links that have been visited by the user), etc.

2. Pseudo elements are more like child elements of elements, but in fact they are not part of the real DOM tree. Pseudo elements allow you to apply styles to specific parts of an element without adding additional HTML markup. For example, the :before and :after pseudo-elements can be used to insert content or styles before and after an element's content.

p:before {  
    content: "Hello, ";  
}  
  
p:after {  
    content: "world!";  
}

In this example, the text "Hello," will be inserted in front of each paragraph (

element), and the text "world!" will be inserted after it. Note that the content attribute is required and defines the content of the pseudo element.

In addition to :before and :after, there are some other commonly used pseudo-elements, such as :first-letter (select the first letter of the element) and :first-line (select the first line of the element) .

In general, pseudo-classes and pseudo-elements provide a flexible way to select and style specific elements or element states, and they are very useful tools in CSS.

The above is the detailed content of What are pseudo-classes and pseudo-elements in css. For more information, please follow other related articles on the PHP Chinese website!