Why use double pseudo-elements to clear floats?

Use double pseudo-elements to clear floats because pseudo-elements can select and operate elements in HTML that cannot be directly selected. By using pseudo-elements, you can create additional layout elements, modify default element styles, solve layout problems, increase page accessibility, and achieve some special effects. The double pseudo-element method of clearing floats is a solution that is easy to use, has good compatibility, is highly flexible and has good scalability. In actual development, a suitable float clearing method can be selected based on project requirements and actual conditions.

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

In front-end development, the double pseudo-element method is usually used to clear floats. This is because pseudo-elements allow us to select and operate elements in HTML that cannot be directly selected. By using pseudo-elements, we can create additional layout elements, modify default element styles, solve layout problems, increase page accessibility, and achieve some special effects.

Clearing floats is a common scenario when using pseudo elements. Floating allows elements to break out of the normal document flow and line up together horizontally. However, this arrangement may cause the height of the parent element to collapse, that is, the height of the parent element is no longer determined by its content, but by the child elements floating inside it. To solve this problem, we can use pseudo elements to clear floats.

The method of clearing floating double pseudo elements usually includes the following steps:

1. Set the overflow attribute to auto or hidden in the CSS style of the parent element, which can prevent the height of the parent element from collapsing.

2. Set the display attribute to flex or grid in the CSS style of the parent element, which can make the parent element have flexible layout characteristics.

3. Use the flex-grow attribute in the CSS style of the parent element and set its value to 1. This allows the parent element to allocate remaining space as needed.

4. Use the flex-basis attribute in the CSS style of the parent element and set its value to 0. This specifies the base size of the child elements and takes this value into account when allocating remaining space.

5. Use the pseudo element ::before or ::after in the CSS style of the child element, and set its content attribute to "". This creates a dummy node for clearing floats.

6. Use the clear attribute in the CSS style of the child element, and set its value to both or left or right, and choose which side of the float to clear as needed.

The method of using double pseudo-elements to clear floats can effectively solve the problems caused by floating, and has the following advantages:

1. Simple and easy to use: The method of using double pseudo-elements to clear floats only requires Several properties need to be set in the CSS style of the parent element without adding additional tags or modifying the HTML structure.

2. Good compatibility: The double pseudo-element clearing floating method has good compatibility in different browsers and does not require the use of additional browser prefixes or compatibility solutions.

3. High flexibility: Using double pseudo-elements to clear floats can flexibly control the direction and range of floats, and you can choose which side of the floats to clear as needed.

4. Good scalability: The double pseudo-element clearing floating method can be applied to various scenarios and layout methods. This method can be used in both responsive layout and fixed layout.

It should be noted that although the double pseudo-element clearing float method is a common solution, it may cause some problems in some cases. For example, if you use flex layout for layout and want to have a nested float layout inside the parent element, then using double pseudo-elements to clear the floats may cause some unintended effects. In this case, you can consider using other techniques to solve the floating problem, such as using the characteristics of flex layout itself instead of floating layout.

To sum up, the reason why double pseudo-elements are used to clear floats is because pseudo-elements allow us to select and operate elements in HTML that cannot be directly selected, and the method of clearing floats with double pseudo-elements is a simple Easy-to-use, compatible, flexible and scalable solution. In actual development, a suitable float clearing method can be selected based on project requirements and actual conditions.

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