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Analysis on CSS horizontal centering

高洛峰Original: 2017-03-08 14:12:281075browse

Horizontal centering is one of the commonly used layout methods. It is mainly divided into centering of inline elements and centering of block elements. The centering of block elements is also divided into fixed-width centering and variable-width centering. The centering of inline elements can be achieved by using text-align:center. The centering of block elements with a known width can be achieved by using absolute positioning and setting

margin to a negative value that is half of the width. However, variable-width centering is more commonly used and more complicated than the above two. We often need to use variable-width centering in pagination page number display and other places. It is more convenient to use. Let’s study the levels of several commonly used block elements. Centered.

1. Label nesting offset

Implementation principle:

Think of the implementation of fixed-width centering: first Offset to the center of the screen, and set its margin direction to offset half the width. So can you think of a way to use this idea to first offset 50% to the right half of the screen, and then offset it back in the opposite direction? The more difficult thing to implement is not knowing what the width is. I also thought that as long as the width of the parent and the width of the child are equal, then using a percentage can solve the problem. So how to make its parent width the same as the word width? Taking advantage of the wrapping property of float: if the parent element is floated and the width and height are not set, it will try to wrap the child elements as much as possible.

Implementation code:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>不定宽度水平居中</title>
    <style>
        body{  
            background-color: #e5da31;  
        }  
        .container{  
            position: absolute;   /*脱离文档流，其宽度将由子元素的宽度决定*/  
            left:50%;  
        }  
        .content{  
            position: absolute;  
            left:-50%;  
            background-color: #2ecc71;  
        }  
    </style>
</head>
<body>
<p class="container">
    <p class="content">标签嵌套</p>
</p>
</body>
</html>

Implementation effect:

Analysis on CSS horizontal centering

Advantages and disadvantages:

The disadvantage is obvious. You need to write tags that have nothing to do with the document content. The compatibility is good after a few extra lines of code. There is no problem viewing it on IE6+ browser

2.flex-box layout

##Implementation principle:

First define a flex container, and then set its content alignment to middle alignment

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>不定宽度水平居中</title>
    <style>
        body {  
            background-color: #e5da31;  
        }  
        .container {  
            display: flex;  /*定义一个flex容器*/  
            justify-content: center;  /*定义容器的空间没有被全部占用时，内容的对其方式*/  
        }  
        .content{  
            background-color: #2ecc71;  
        }  
    </style>
</head>
<body>
<p class="container">
    <p class="content">标签嵌套</p>
</p>
</body>
</html>

Achievement effect:

Analysis on CSS horizontal centering

Analysis of advantages and disadvantages:

is the simplest to implement, but because of flex compatibility The performance is not good, so use it with caution when it needs to be compatible with low-end browsers.

3. Inline layout

Implementation principle:

text-align:center can center the inline elements horizontally. If you change the block element to an inline element, you can use text-align to achieve horizontal centering.

Implementation code:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>不定宽度水平居中</title>
    <style>
        body{  
            background-color: #e5da31;  
        }  
        .container{  
          text-align:center;  
        }  
        .content{  
        display: inline;  
            background-color: #2ecc71;  
        }  
    </style>
</head>
<body>
<p class="container">
    <p class="content">标签嵌套</p>
</p>
</body>
</html>

Implementation effect:

Analysis on CSS horizontal centering

Analysis of advantages and disadvantages:

It always feels a bit awkward to use text-align, which is originally used to modify text alignment, to achieve horizontal centering. The outer container is also redundant, but in order not to affect other elements in the body Partially, for now. In addition, the compatibility is good and can be displayed normally in IE6+.

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