Detailed explanation of how to clear floats using CSS

This article mainly introduces the detailed method of using CSS to clear floats. It is worth noting that not simply clearing floats can solve related problems every time. The solution of closing floats mentioned at the end of the article is also worth a try. , Friends in need can refer to

Clear floating method
Method 1: Use an empty element with clear attribute

Use an empty element after the floating element, such as

.news {   
  background-color: gray;   
  border: solid 1px black;   
  }   

.news img {   
  float: left;   
  }   

.news p {   
  float: rightright;   
  }   

.clear {   
  clear: both;   
  }

<p class="news">
<img  src="news-pic.jpg" / alt="Detailed explanation of how to clear floats using CSS" >
<p>some text</p>
<p class="clear"></p>
</p>

Advantages: simple, less code, good browser compatibility.
Disadvantages: A large number of unsemantic html elements need to be added, the code is not elegant enough, and it is not easy to maintain later.

Method 2: Use the overflow attribute of CSS

Add overflow:hidden; or overflow:auto; to the container of the floating element to clear the float. In addition, in IE6 HasLayout needs to be triggered, such as setting the container width and height for the parent element or setting zoom:1. After adding the overflow attribute, the floating element returns to the container layer, raising the height of the container, achieving the effect of cleaning up the floating elements.

.news {   
  background-color: gray;   
  border: solid 1px black;   
  overflow: hidden;   
  *zoom: 1;   
  }   

.news img {   
  float: left;   
  }   

.news p {   
  float: rightright;   
  }

<p class="news">
<img  src="news-pic.jpg" / alt="Detailed explanation of how to clear floats using CSS" >
<p>some text</p>
</p>

Method 3: Add a float to the container of the floating element

Also add a floating attribute to the container of the floating element to clear the interior Float, but this will make it float as a whole and affect the layout, so it is not recommended.

Method 4: Use adjacent element processing

Do nothing and add the clear attribute to the element behind the floating element.

.news {   
  background-color: gray;   
  border: solid 1px black;   
  }   

.news img {   
  float: left;   
  }   

.news p {   
  float: rightright;   
  }   

.content{   
  clear:both;   
  }

<p class="news">
<img  src="news-pic.jpg" / alt="Detailed explanation of how to clear floats using CSS" >
<p>some text</p>
<p class="content">***</p>
</p>

Note that p.content here has content.

Method Five: Use CSS:after pseudo-element

Combined with:after pseudo-element (note that this is not a pseudo-class, but a pseudo-element, which represents the nearest element after elements) and IEhack, which are perfectly compatible with all major current mainstream browsers. IEhack here refers to triggering hasLayout.
Add a clearfix class to the container of floating elements, and then add an :after pseudo-element to this class to add an invisible block element (Block element) to the end of the element to clean up the floating elements.

.news {   
  background-color: gray;   
  border: solid 1px black;   
  }   

.news img {   
  float: left;   
  }   

.news p {   
  float: rightright;   
  }   

.clearfix:after{   
  content: "020";    
  display: block;    
  height: 0;    
  clear: both;    
  visibility: hidden;     
  }   

.clearfix {   
  /* 触发 hasLayout */
  zoom: 1;    
  }

<p class="news clearfix">
<img  src="news-pic.jpg" / alt="Detailed explanation of how to clear floats using CSS" >
<p>some text</p>
</p>

Add an invisible space "020" or dot "." at the end of the internal element of the container through CSS pseudo-elements, and assign the clear attribute to clear the float. It should be noted that for IE6 and IE7 browsers, a zoom:1; must be added to the clearfix class to trigger haslayout.

Summary
Through the above example, we can easily find that the methods of clearing floats can be divided into two categories:

One is to use the clear attribute, included in the floating element Add an empty p with the clear: both attribute at the end to close the element. In fact, the method of using the :after pseudo-element is also achieved by adding an element with the content of a dot and the clear: both attribute at the end of the element.

The second is to trigger the BFC (Block Formatting Contexts, block-level formatting context) of the parent element of the floating element, so that the parent element can contain floating elements. Regarding this point.

Use the :after pseudo-element method in the main layout of the web page and use it as the main way to clean up floats; use overflow:hidden; in small modules such as ul (pay attention to possible hidden overflow element problems); if it is a float itself Elements can automatically clear internal floats without special processing; use adjacent elements in the body to clear previous floats.

Finally, you can use the relatively perfect :after pseudo-element method to clean up the floats, making the document structure clearer.

Postscript: Clear float or close float?
We often use floats in web page layout. With it, we can more easily achieve the effects we want, but floats often leave some hidden dangers. At this time, we usually do one thing to clear the floats, but clearing the floats often leaves hidden dangers. The following code:

<!DOCTYPE html>   
<html>   
<head>   
    <meta charset="UTF-8">   
    <title>Document</title>   
    <style type=&#39;text/css&#39;>   
        #main{   
            border: 1px solid #000;   
        }   
        #left{   
            float: left;   
            width: 100px;   
            height: 100px;   
            background-color: #f00;   
        }   
        #right{   
            float: left;   
            width: 100px;   
            height: 100px;   
            background-color: #0f0;   
        }   
    </style>   
</head>   
<body>   
    <p id="main">   
        <p id="left"></p>   
        <p id="right"></p>   
    </p>   
</body>   
</html>

The rendering is as follows:

Although clear:both is used in foot to clear floats, the height of main cannot adapt to the height of sub-elements, resulting in collapse (pointed by the arrow).

The following introduces closed float. As the name suggests, it is to close the floating element and clear the impact of floating. Currently, the most commonly used method to clear floats is clearfix. Specifically, there is no need to add clear:both in the foot, insert the following line of css:

#main:after{   
            content: '.';   
            height: 0;   
            visibility: hidden;   
            /*display: block;*/
            clear:both;   
        }

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