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左边框 | 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

代码语言:javascript
复制
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......

代码语言:javascript
复制
border-left-style: dotted;
border-left: thick green;

实际上应该是下面这个样子:

代码语言:javascript
复制
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: border-left-width: medium border-left-style: none border-left-color: currentcolor

适用元素

all elements. It also applies to ::first-letter.

是否是继承属性

no

适用媒体

visual

计算值

as each of the properties of the shorthand: border-left-width: the absolute length or 0 if border-left-style is none or hidden border-left-style: as specified border-left-color: computed color

Animation type

as each of the properties of the shorthand: border-left-color: a color border-left-style: discrete border-left-width: a length

正规顺序

order of appearance in the formal grammar of the values

  • border-left-widthmedium
  • border-left-stylenone
  • border-left-colorcurrentcolor
代码语言:txt
复制
Applies to all elements. It also applies to [`::first-letter`](::first-letter).   [Inherited](inheritance) no   Media visual   [Computed value](computed_value) as each of the properties of the shorthand:
  • border-left-width:绝对长度或0如果border-left-stylenonehidden
  • border-left-style:具体规定
  • border-left-color:计算颜色
代码语言:txt
复制
Animation type as each of the properties of the shorthand:
  • border-left-color:颜色
  • border-left-style:离散
  • border-left-width:长度
代码语言:txt
复制
Canonical order order of appearance in the formal grammar of the values  

语法

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。

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

正式语法

代码语言:javascript
复制
<br-width> || <br-style> || <color>where 
<br-width> = <length> | thin | medium | thick
<br-style> = none | hidden | dotted | dashed | solid | double | groove | ridge | inset | outset
<color> = <rgb()> | <rgba()> | <hsl()> | <hsla()> | <hex-color> | <named-color> | currentcolor | <deprecated-system-color>
where 
<rgb()> = rgb( [ [ <percentage>{3} | <number>{3} ] [ / <alpha-value> ]? ] | [ [ <percentage>#{3} | <number>#{3} ] , <alpha-value>? ] )
<rgba()> = rgba( [ [ <percentage>{3} | <number>{3} ] [ / <alpha-value> ]? ] | [ [ <percentage>#{3} | <number>#{3} ] , <alpha-value>? ] )
<hsl()> = hsl( [ <hue> <percentage> <percentage> [ / <alpha-value> ]? ] | [ <hue>, <percentage>, <percentage>, <alpha-value>? ] )
<hsla()> = hsla( [ <hue> <percentage> <percentage> [ / <alpha-value> ]? ] | [ <hue>, <percentage>, <percentage>, <alpha-value>? ] )
where 
<alpha-value> = <number> | <percentage>
<hue> = <number> | <angle>

示例

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

规范

Specification

Status

Comment

CSS Backgrounds and Borders Module Level 3The definition of 'border-left' in that specification.

Candidate Recommendation

No direct changes, though the modification of values for the border-left-color do apply to it.

CSS Level 2 (Revision 1)The definition of 'border-left' in that specification.

Recommendation

No significant changes.

CSS Level 1The definition of 'border-left' in that specification.

Recommendation

Initial definition.

浏览器兼容性

Feature

Chrome

Edge

Firefox (Gecko)

Internet Explorer

Opera

Safari (WebKit)

Basic support

1.0

(Yes)

1.0 (1.7 or earlier)

4

3.5

1.0 (85)

Feature

Android

Edge

Firefox Mobile (Gecko)

IE Phone

Opera Mobile

Safari Mobile

Basic support

1.0

(Yes)

1.0 (1.0)

(Yes)

(Yes)

(Yes)

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