Why can pseudo elements clear floats?

The reason why pseudo elements can clear floats is because pseudo elements can create a new BFC. BFC is an independent rendering area in which the elements are laid out according to certain rules. Pseudo-elements are a concise and flexible solution. By creating a pseudo-element on the parent element of a floated element and setting it to "display: table;", you can turn the parent element into a BFC. This way, the parent element can contain the floated element and not be affected by the floated element.

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

Floating is one of the commonly used layout techniques in CSS. It can make elements break away from the document flow, thereby achieving multi-column layout, mixed graphics and text, etc. However, floating elements can have an impact on other elements, making them unable to layout properly. To solve this problem, we can use the clear float method. Among them, pseudo elements are a common technique for clearing floats.

Pseudo element is a special element in CSS. It does not need to be defined in HTML, but is created and controlled through CSS selectors. Common pseudo-elements include ::before and ::after. These pseudo-elements can insert additional content before and after the content of the element, and the display and layout of this content can be controlled through CSS styles.

The reason why pseudo-elements can clear floats is because they can create a new BFC (block-level format context). BFC is a concept in CSS. It is an independent rendering area in which elements are laid out according to certain rules. BFC has the following characteristics:

1. The elements in BFC are arranged vertically and will not overlap each other even if their floating attributes are different.

2. The elements in BFC will not overlap with floating elements, but will occupy as much space as possible.

3. Elements in the BFC will not affect the layout of external elements, even if they float or overflow the BFC.

By creating a pseudo-element on the parent element of a floating element and setting it to display: table;, you can turn the parent element into a BFC. This way, the parent element can contain the floated element and not be affected by the floated element. The specific code is as follows:

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

In the above code, the ::after pseudo-element is inserted after the content of the .parent element and is set to display: table;. The clear: both; attribute is used to clear floats so that the parent element can be laid out normally. In this way, even if the .parent element contains floating elements, it will not cause the parent element to collapse or overflow.

In addition to using pseudo elements to clear floats, there are other ways to achieve the same effect, such as using the clearfix class or setting the overflow: hidden; attribute to the parent element. However, pseudo-elements are a concise and flexible solution that does not require adding additional HTML elements or modifying CSS styles, and can be easily applied to various scenarios.

In summary, pseudo-elements can clear floats because they can create a new BFC so that the parent element can contain floated elements and not be affected by them. The effect of clearing the float can be achieved by inserting a pseudo element on the parent element of the floated element and setting it to display: table;. Pseudo elements are a concise and flexible solution that can be easily applied to various layout scenarios.

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