How to clear float in css3

CSS3 clear float

During web development, float is a very common CSS property used for layout. Floating allows elements to escape the flow of the document and be placed freely on the page as needed. But floating also has a problem, that is, it may cause elements to overlap or cause the height of the parent element to collapse. To solve this problem, we need to use some tricks to clear the floats.

1. What is float

In CSS, float means floating. It is a method of positioning elements. When an element has the float attribute set, it breaks out of the document flow and moves left or right until its outer edge touches the edge of its containing element or the edge of another floated element.

2. Problems with Floating

Although floating allows elements to be placed freely, it can also cause some problems. For example, floating elements will cause the height of the parent element to collapse. This problem can be solved by setting the overflow attribute to the parent element. At the same time, floating will also cause elements to overlap. This problem can be solved by using the clear attribute.

3. Methods of clearing floats

1. Use the clear attribute

In CSS, the clear attribute is used to clear floating attributes. It has four values, namely left, right, both and none. Among them, left means clearing left floats, right means clearing right floats, both means clearing left and right floats, and none means not clearing any floats.

For example:

.clearfix { clear: both; }

In this example, we use a clearfix class to clear floats. In HTML, we can add this class to the elements that need to clear floats:

<div>
  <div></div>
  <div></div>
</div>

2. Use empty elements

In addition to the clear attribute, we can also use an empty element to clear floats.

<div>
  <div></div>
  <div></div>
  <div></div>
</div>

In this example, we use an empty element to clear the float. This element does not appear on the page, but it will occupy space under the floated element, thereby preventing overlapping and height collapse of the parent element.

3. Use the box model

In CSS3, we can use the box-sizing attribute to clear floating. box-sizing has two values, namely content-box and border-box. Among them, content-box means that the width and height of the element only include the width and height of the content, while border-box means that the width and height of the element include the width and height of the content and the width of the border.

For example:

.clearfix {
  box-sizing: border-box;
  padding: 10px;
  border: 1px solid #ccc;
}

In this example, we use box-sizing to clear floats. Since the border-box is set, padding and border will not change the size of the element, thus avoiding the problems of overlapping floating elements and height collapse of parent elements.

4. Summary

Through the above introduction, we understand what floating is and the problems caused by floating. At the same time, we also learned three methods of clearing floats, namely using the clear attribute, using empty elements and using the box model. In actual projects, we can choose the appropriate float clearing method according to the actual situation.

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