Usage of border-sizing attribute in css-CSS Tutorial-php.cn

Usage of border-sizing attribute in css

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Release： 2018-07-28 09:59:48

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This article introduces to you the article content about the usage of border-sizing attribute in CSS. It has a good reference value. I hope it can help friends in need.

box-sizing is used to change the default CSS box model used to calculate the width and height of elements. It has three values: content-box, border-box and inherit. Inherit refers to inheriting the box-sizing form from the parent element, which is no longer redundant.

## 1. Attribute explanation

#content-box
The default value is also the box model in CSS2.1. When calculating width and height, border, padding and margin are not calculated. Height and width are just the content height

#border-boxcss3New. The width and

height

properties include content, padding, and borders, but not margins.

Calculation formula:

##width = width = border padding Content width
height = border padding content height

## 2. Consider the margin
of the box model. From the above, we can know that even border-box is the same margin is not calculated, but border and padding are calculated redundantly. Because border and padding are both part of the box model, but margin marks the distance between boxes . Therefore, the explanation of border-box

is very common sense.

The question is, if margin must be set sometimes, how can it be freely controlled to ensure compatibility? For example, we want to set up a box element that fills the entire page and is interfered with by margins. How should we do this?

Achieve the following effect diagram: Usage of border-sizing attribute in css

Code:

Source code download

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>yuanxin.me</title>
  <style type="text/css">
    *{
      margin: 0;
      padding: 0;
    }
    #app {
      box-sizing: border-box; /* 指定计算方式 */
      margin: 10px; /* 外边距干扰 */
      /* 利用 css3 的 calc */
      width: calc(100vw - 2*10px);
      height: calc(100vh - 2*10px);
    }
  </style>
</head>
<body>
  <p id="app">
  </p>
</body>
</html>

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So, when you need to calculate the margin (margin), you can use with the four arithmetic operations (calc

) in css3.

## 3. Usage suggestions

Based on the experience in the project and the recommendations of w3c, it is recommended to set the box-sizing attribute to border-box.

* {
  margin: 0;
  padding: 0;
}
p {
  box-sizing: border-box;
}

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