In-depth discussion on the use of CSS pseudo-elements before and after

CSS pseudo-elements before and after are a way to add styles before and after HTML elements. These two CSS pseudo-elements are mainly used to add decorative elements or add additional styles to text. In this article, we’ll explore the use of the CSS pseudo-elements before and after and provide some practical examples.

1. Usage of CSS pseudo-elements before and after

The syntax is as follows:

选择器:before{ content: ""; /* 插入内容 */ 属性:属性值; }
选择器:after{ content: ""; /* 插入内容 */ 属性:属性值; }

Among them, the selector refers to the element selector that needs to insert decorative elements, before and after is a pseudo element. In the above syntax, the value of the content attribute is used to insert content (such as text, pictures, etc.). In addition, pseudo-elements before and after can also use other style attributes, such as color, background, border, etc.

2. Add text prefixes and suffixes

One of the most common uses of CSS pseudo-elements before and after is to add prefixes and suffixes to text. For example, we can use the pseudo-element before to place the small icon before the text, as shown below:

HTML code:

<p>下面是一些列表项：</p>
<ul>
  <li>CSS</li>
  <li>HTML</li>
  <li>JavaScript</li>
</ul>

CSS code:

li:before{
  content: url('icon.png');
  margin-right: 5px;
}

In this way, we You can add a small icon in front of the list item.

You can also use the pseudo element after to add content after the text. For example, we can add a "/" symbol to each table cell in an HTML table with the following code:

HTML code:

<table>
  <tr>
    <td>苹果</td>
    <td>橘子</td>
    <td>香蕉</td>
  </tr>
</table>

CSS code:

td:after{
  content: "/";
  margin-left: 5px;
}

三, Create a slider

CSS pseudo-elements before and after can also be used to create a slider. For example, we can create a slider button with sliding animation, the code is as follows:

HTML code:

<button class="slider">Slide to Unlock</button>

CSS code:

.slider{
  width: 200px;
  height: 50px;
  border: none;
  background-color: #0084FF;
  color: #FFF;
  position: relative;
  overflow: hidden;
  cursor: pointer;
  font-size: 1.2em;
}
.slider:before{
  content: "";
  display: block;
  position: absolute;
  width: 50px;
  height: 50px;
  background: #FFF;
  top: 0;
  left: -5px;
  border-radius: 50%;
  transform: translateX(-100%) rotate(45deg);
  animation: slider 1s infinite;
}
@keyframes slider{
  0%{
    transform: translateX(-100%) rotate(45deg);
  }
  50%{
    transform: translateX(100%) rotate(45deg);
  }
  100%{
    transform: translateX(-100%) rotate(45deg);
  }
}

4. Create a dog-ear effect

Another common way to use the CSS pseudo-elements before and after is to create a dog-ear effect. For example, on the homepage title of the website, we can use the pseudo elements before and after to create a dog-ear effect. The code is as follows:

HTML code:

<h1>Welcome to My Website</h1>

CSS code:

h1{
  position: relative;
  text-align: center;
  color: #FFF;
  background-color: #0084FF;
  padding: 20px;
  margin: 0;
}
h1:before, h1:after{
  content: "";
  position: absolute;
  bottom: -20px;
  border: 20px solid transparent;
}
h1:before{
  border-top-color: #0084FF;
  left: 0;
}
h1:after{
  border-top-color: #0084FF;
  right: 0;
}

The above are several uses of CSS pseudo elements before and after. Whether you're adding prefixes and suffixes to text, creating slider buttons, or creating a dog-ear effect, the CSS pseudo-elements before and after can add some new visual elements to your website. This way you can change the style and layout without adding HTML code, making your website more visually appealing.

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