Why use double pseudo-element removal method?

The reason for using the double pseudo-element clearing method is that it can effectively solve the layout problems caused by floating elements and ensure that the parent element correctly calculates its height. In CSS, floating elements will break away from the normal document flow, which may cause the parent element to fail to calculate its height correctly, causing layout problems. The double pseudo-element clearing method is a common method to solve this problem. The principle of using the double pseudo-element clearing method is to insert two empty pseudo-elements after the floating element, and set these two pseudo-elements as block-level elements, etc.

# Operating system for this tutorial: Windows 10 system, Dell G3 computer.

Double Pseudo Element Clearing Method is a technique for clearing floating elements. In CSS, floating elements break out of the normal document flow, potentially causing the parent element to not calculate its height correctly, causing layout issues. Double pseudo-element cleaning is a common method to solve this problem.

The principle of using the double pseudo-element clearing method is to insert two empty pseudo-elements after the floating element and set these two pseudo-elements as block-level elements. In this way, these two pseudo-elements will extend the height of the parent element, thereby solving the problem that the parent element cannot correctly calculate the height.

The following is a sample code using the double pseudo-element clearing method:

.clearfix::after {
  content: "";
  display: table;
  clear: both;
}
.clearfix::before {
  content: "";
  display: table;
}

In the above code, the `.clearfix` class selector is used to select the parent element that needs to be cleared of floats. By using the `::after` pseudo-element and the `content: "";` attribute, we insert an empty pseudo-element at the end of the parent element. Then, set the pseudo-element as a block-level element by setting the `display: table;` attribute, and clear the float using the `clear: both;` attribute.

To ensure the correct display of the pseudo-element, we also add an empty `::before` pseudo-element and set it as a block-level element. This is because some older versions of IE may not properly handle the clearing technique of only the `::after` pseudo-element.

Using the double pseudo-element clearing method can effectively solve layout problems caused by floating elements and ensure that the parent element correctly calculates its height. However, with the development of CSS layout technology, now a more common way to solve the floating problem is to use Flexbox or Grid layout, which provide more flexible and powerful layout functions. Therefore, in actual development, you may be more inclined to use these new layout techniques to solve layout problems rather than relying on the double pseudo-element clearing method.

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