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border-left

CSS 属性 border-left 是属性border-left-color, border-left-style, 和border-left-width的三者的缩写。这些属性都是在描述一个元素的左边的边框border。

border-left: 1px;
border-left: 2px dotted;
border-left: medium dashed green;

这三种属性值的缩写需要按照顺序定义数值，也可以省略其中的一个或者两个。

和 CSS 所有的缩写属性一样，border-left 总是会设置该缩写属性所包含的全部属性值，即使开发者并没有一一指定这些值。CSS 缩写属性会给没有被定义的属性一个默认的属性值。那就意味着下面这个例子......

border-left-style: dotted;
border-left: thick green;

......实际上应该是下面这个样子......

border-left-style: dotted;
border-left: none thick green;

......并且在 border-left 之前定义的 border-left-style 的值也会被覆盖。由于 border-left-style 的默认值是 none, border-style 的最终结果就是没有边框。

初始值as each of the properties of the shorthand:
适用元素all elements. It also applies to ::first-letter.
是否是继承属性否
计算值as each of the properties of the shorthand:
Animation typeas each of the properties of the shorthand:

Syntax

这三种属性值的缩写需要按照顺序定义数值，也可以省略其中的一个或者两个。

Values

<br-width> 
请参阅border-left-width.
<br-style> 
请参阅border-left-style.
<color>
请参阅 border-left-color.

Formal syntax

border-left = 
  <line-width>  ||
  <line-style>  ||
  <color>       

<line-width> = 
  <length [0,∞]>  |
  thin            |
  medium          |
  thick           

<line-style> = 
  none    |
  hidden  |
  dotted  |
  dashed  |
  solid   |
  double  |
  groove  |
  ridge   |
  inset   |
  outset  

<color> = 
  <absolute-color-base>  |
  currentcolor           |
  <system-color>         |
  <device-cmyk()>        

<absolute-color-base> = 
  <hex-color> (en-US)    |
  <named-color>  |
  transparent    |
  <rgb()>        |
  <rgba()>       |
  <hsl()>        |
  <hsla()>       |
  <hwb()>        |
  <lab()>        |
  <lch()>        |
  <oklab()>      |
  <oklch()>      |
  <color()>      

<device-cmyk()> = 
  device-cmyk( <cmyk-component>{4} [ / <alpha-value> ]? )  

<rgb()> = 
  rgb( [ <percentage> | none ]{3} [ / [ <alpha-value> | none ] ]? )  |
  rgb( [ <number> | none ]{3} [ / [ <alpha-value> | none ] ]? )      

<hsl()> = 
  hsl( [ <hue> | none ] [ <percentage> | none ] [ <percentage> | none ] [ / [ <alpha-value> | none ] ]? )  

<hwb()> = 
  hwb( [ <hue> | none ] [ <percentage> | none ] [ <percentage> | none ] [ / [ <alpha-value> | none ] ]? )  

<lab()> = 
  lab( [ <percentage> | <number> | none ] [ <percentage> | <number> | none ] [ <percentage> | <number> | none ] [ / [ <alpha-value> | none ] ]? )  

<lch()> = 
  lch( [ <percentage> | <number> | none ] [ <percentage> | <number> | none ] [ <hue> | none ] [ / [ <alpha-value> | none ] ]? )  

<oklab()> = 
  oklab( [ <percentage> | <number> | none ] [ <percentage> | <number> | none ] [ <percentage> | <number> | none ] [ / [ <alpha-value> | none ] ]? )  

<oklch()> = 
  oklch( [ <percentage> | <number> | none ] [ <percentage> | <number> | none ] [ <hue> | none ] [ / [ <alpha-value> | none ] ]? )  

<color()> = 
  color( <colorspace-params> [ / [ <alpha-value> | none ] ]? )  

<cmyk-component> = 
  <number>      |
  <percentage>  

<alpha-value> = 
  <number>      |
  <percentage>  

<hue> = 
  <number>  |
  <angle>   |
  none      

<colorspace-params> = 
  <predefined-rgb-params>  |
  <xyz-params>             

<predefined-rgb-params> = 
  <predefined-rgb> [ <number> | <percentage> | none ]{3}  

<xyz-params> = 
  <xyz-space> [ <number> | none ]{3}  

<predefined-rgb> = 
  srgb          |
  srgb-linear   |
  display-p3    |
  a98-rgb       |
  prophoto-rgb  |
  rec2020       

<xyz-space> = 
  xyz      |
  xyz-d50  |
  xyz-d65

Example

<div>
  This box has a border on the left side.
</div>
div {
  border-left: 4px dashed blue;
  background-color: gold;
  height: 100px;
  width: 100px;
  font-weight: bold;
  text-align: center;
}

Specifications

Specification Status Comment
CSS Backgrounds and Borders Module Level 3
border-left		 Candidate Recommendation No direct changes, though the modification of values for the border-left-color do apply to it.
CSS Level 2 (Revision 1)
border-left		 Recommendation No significant changes.
CSS Level 1
border-left		 Recommendation Initial definition.

Browser compatibility

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