Parse common uses and examples of CSS pseudo-classes and pseudo-elements

Deeply explore the common usage and example analysis of CSS pseudo-classes and pseudo-elements

In front-end development, CSS is one of our commonly used style design languages. In addition to basic selectors and attributes, CSS also provides some special selectors called pseudo-classes and pseudo-elements. This article will delve into the common usage and example analysis of CSS pseudo-classes and pseudo-elements, and attach specific code examples.

1. Common usage and example analysis of pseudo-classes

1. :hover pseudo-class

:hover pseudo-class is used for mouse hover effect. Sets the style on mouseover on the element. For example, we can create a simple button dynamic effect. The code example is as follows:

<style>
   .btn {
      padding: 10px 20px;
      background-color: #ccc;
      color: #fff;
   }
   .btn:hover {
      background-color: #f00;
   }
</style>
<button class="btn">悬停按钮</button>

In this example, the background color of the button will turn red on hover.

2. :active pseudo-class

:active pseudo-class is used to set styles when the element is activated (clicked). For example, we can create a simple button click effect. The code example is as follows:

<style>
   .btn {
      padding: 10px 20px;
      background-color: #ccc;
      color: #fff;
   }
   .btn:active {
      background-color: #f00;
   }
</style>
<button class="btn">点击按钮</button>

In this example, the background color of the button will turn red when clicked.

3. :nth-child pseudo-class

:nth-child pseudo-class is used to select a child element at a specific position under the parent element. For example, we can set different background colors for odd and even rows in the list. The code example is as follows:

<style>
   li:nth-child(odd) {
      background-color: #ccc;
   }
   li:nth-child(even) {
      background-color: #f00;
   }
</style>
<ul>
   <li>列表项1</li>
   <li>列表项2</li>
   <li>列表项3</li>
   <li>列表项4</li>
</ul>

In this example, the background color of the odd-numbered rows in the list is gray, and the background color of the even-numbered rows is red.

2. Common usage and example analysis of pseudo-elements

1. ::before pseudo-element

::before pseudo-element is used in a certain element Insert an element in front of the content and set styles for it. For example, we can add a tag in front of a paragraph and set a style for it. The code example is as follows:

<style>
   p::before {
      content: "前面插入的元素";
      background-color: #ccc;
   }
</style>
<p>段落内容</p>

In this example, a gray background color will appear in front of the paragraph and the text "Element inserted previously" will be displayed.

2. ::after pseudo-element

::after pseudo-element is used to insert an element after the content of an element and set styles for it. For example, we can add a tag after a paragraph and set a style for it. The code example is as follows:

<style>
   p::after {
      content: "后面插入的元素";
      background-color: #ccc;
   }
</style>
<p>段落内容</p>

In this example, a gray background color will appear after the paragraph and the text "Element inserted after" will be displayed.

3. ::first-letter pseudo-element

::first-letter pseudo-element is used to select the first letter of an element and set styles for it. For example, we can set a special style for the first letter of a paragraph. The code example is as follows:

<style>
   p::first-letter {
      font-size: 24px;
      color: #f00;
   }
</style>
<p>首字母大写的段落内容</p>

In this example, the first letter of the paragraph will turn red and enlarge to 24px font size.

This article deeply explores the common usage and example analysis of pseudo-classes and pseudo-elements in CSS, and attaches specific code examples. By rationally using pseudo-classes and pseudo-elements, we can more flexibly control the style of the page and achieve richer interactive effects and visual effects. I hope this article can be helpful to everyone's front-end development work.

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