css属性 border-top-width
是用于设置盒模型的上边框的宽度
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Syntax
/* Keyword values */
border-top-width: thin;
border-top-width: medium;
border-top-width: thick;
/* <length> values */
border-top-width: 10em;
border-top-width: 3vmax;
border-top-width: 6px;
/* Global keywords */
border-top-width: inherit;
border-top-width: initial;
border-top-width: unset;
Values
<br-width>
- 上边框的宽度属性的有效值要么是一个具体的非负数,要么是一个关键字。如果是关键字,必须是一下几种:
thin
A thin border medium
A medium border thick
A thick border Note: Because the specification doesn't define the exact thickness denoted by each keyword, the precise result when using one of them is implementation-specific. Nevertheless, they always follow the pattern
thin ≤ medium ≤ thick
, and the values are constant within a single document.
Formal syntax
Example
HTML
<div>Element 1</div>
<div>Element 2</div>
CSS
div {
border: 1px solid red;
margin: 1em 0;
}
div:nth-child(1) {
border-top-width: thick;
}
div:nth-child(2) {
border-top-width: 2em;
}
Result
Specifications
Specification | Status | Comment |
---|---|---|
CSS Backgrounds and Borders Module Level 3 border-top-width |
Candidate Recommendation | No significant change. |
CSS Level 2 (Revision 1) border-top-width |
Recommendation | No significant change. |
CSS Level 1 border-top-width |
Recommendation | Initial definition. |
初始值 | medium |
---|---|
适用元素 | all elements. It also applies to ::first-letter . |
是否是继承属性 | 否 |
计算值 | the absolute length or 0 if border-top-style is none or hidden |
Animation type | a length |
Browser compatibility
BCD tables only load in the browser
The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
See also
- The other border-width-related CSS properties:
border-left-width
,border-right-width
,border-bottom-width
, andborder-width
. - The other border-top-related CSS properties:
border
,border-top
,border-top-style
, andborder-top-color
.