Added in v5.3
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链接（Link）
链接工具可用于调整锚点的颜色、不透明度、下划线偏移、下划线颜色等。
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链接不透明度
使用实用程序更改链接 rgba() 颜色值的 alpha 不透明度。请注意，更改颜色的不透明度可能导致链接的对比度不足。
<p><a class="link-opacity-10" href="#">Link opacity 10</a></p>
<p><a class="link-opacity-25" href="#">Link opacity 25</a></p>
<p><a class="link-opacity-50" href="#">Link opacity 50</a></p>
<p><a class="link-opacity-75" href="#">Link opacity 75</a></p>
<p><a class="link-opacity-100" href="#">Link opacity 100</a></p>您甚至可以改变悬停时的不透明度。
<p><a class="link-opacity-10-hover" href="#">Link hover opacity 10</a></p>
<p><a class="link-opacity-25-hover" href="#">Link hover opacity 25</a></p>
<p><a class="link-opacity-50-hover" href="#">Link hover opacity 50</a></p>
<p><a class="link-opacity-75-hover" href="#">Link hover opacity 75</a></p>
<p><a class="link-opacity-100-hover" href="#">Link hover opacity 100</a></p>链接下划线
下划线颜色
改变下划线的颜色，使其与链接文本颜色无关。
<p><a href="#" class="link-underline-primary">Primary underline</a></p>
<p><a href="#" class="link-underline-secondary">Secondary underline</a></p>
<p><a href="#" class="link-underline-success">Success underline</a></p>
<p><a href="#" class="link-underline-danger">Danger underline</a></p>
<p><a href="#" class="link-underline-warning">Warning underline</a></p>
<p><a href="#" class="link-underline-info">Info underline</a></p>
<p><a href="#" class="link-underline-light">Light underline</a></p>
<p><a href="#" class="link-underline-dark">Dark underline</a></p>下划线偏移
改变下划线与文本的距离。偏移量以 em 为单位设置，可根据元素当前的 font-size 自动缩放。
<p><a href="#">Default link</a></p>
<p><a class="link-offset-1" href="#">Offset 1 link</a></p>
<p><a class="link-offset-2" href="#">Offset 2 link</a></p>
<p><a class="link-offset-3" href="#">Offset 3 link</a></p>下划线不透明
更改下划线的不透明度。需要添加 .link-underline，首先设置一个 rgba() 颜色，然后再修改 alpha 不透明度。
<p><a class="link-offset-2 link-underline link-underline-opacity-0" href="#">Underline opacity 0</a></p>
<p><a class="link-offset-2 link-underline link-underline-opacity-10" href="#">Underline opacity 10</a></p>
<p><a class="link-offset-2 link-underline link-underline-opacity-25" href="#">Underline opacity 25</a></p>
<p><a class="link-offset-2 link-underline link-underline-opacity-50" href="#">Underline opacity 50</a></p>
<p><a class="link-offset-2 link-underline link-underline-opacity-75" href="#">Underline opacity 75</a></p>
<p><a class="link-offset-2 link-underline link-underline-opacity-100" href="#">Underline opacity 100</a></p>悬停变体
与.link-opacity-*-hover工具一样，.link-offset和.link-underline-opacity工具默认包含:hover变体。混合和匹配可创建独特的链接样式。
<a class="link-offset-2 link-offset-3-hover link-underline link-underline-opacity-0 link-underline-opacity-75-hover" href="#">
Underline opacity 0
</a>彩色链接
彩色链接助手已更新，可与我们的链接实用程序配对使用。使用新工具可以修改链接不透明度、下划线不透明度和下划线偏移量。
<p><a href="#" class="link-primary link-offset-2 link-underline-opacity-25 link-underline-opacity-100-hover">Primary link</a></p>
<p><a href="#" class="link-secondary link-offset-2 link-underline-opacity-25 link-underline-opacity-100-hover">Secondary link</a></p>
<p><a href="#" class="link-success link-offset-2 link-underline-opacity-25 link-underline-opacity-100-hover">Success link</a></p>
<p><a href="#" class="link-danger link-offset-2 link-underline-opacity-25 link-underline-opacity-100-hover">Danger link</a></p>
<p><a href="#" class="link-warning link-offset-2 link-underline-opacity-25 link-underline-opacity-100-hover">Warning link</a></p>
<p><a href="#" class="link-info link-offset-2 link-underline-opacity-25 link-underline-opacity-100-hover">Info link</a></p>
<p><a href="#" class="link-light link-offset-2 link-underline-opacity-25 link-underline-opacity-100-hover">Light link</a></p>
<p><a href="#" class="link-dark link-offset-2 link-underline-opacity-25 link-underline-opacity-100-hover">Dark link</a></p>
<p><a href="#" class="link-body-emphasis link-offset-2 link-underline-opacity-25 link-underline-opacity-75-hover">Emphasis link</a></p>
可用性提示： 使用颜色来增加含义，只能提供视觉指示，无法传达给屏幕阅读器等辅助技术的用户。请确保从内容本身（例如，具有足够色彩对比度 的可见文本）或通过其他方式（例如使用
.visually-hidden类隐藏的附加文本）明显看出含义。
CSS
除了以下 Sass 功能外，还可以考虑阅读我们的 CSS 自定义属性（又称 CSS 变量），以了解颜色等方面的信息。
Sass utilities API
链接实用程序在 scss/_utilities.scss 中的实用程序 API 中声明。了解如何使用实用程序 API
"link-opacity": (
css-var: true,
class: link-opacity,
state: hover,
values: (
10: .1,
25: .25,
50: .5,
75: .75,
100: 1
)
),
"link-offset": (
property: text-underline-offset,
class: link-offset,
state: hover,
values: (
1: .125em,
2: .25em,
3: .375em,
)
),
"link-underline": (
property: text-decoration-color,
class: link-underline,
local-vars: (
"link-underline-opacity": 1
),
values: map-merge(
$utilities-links-underline,
(
null: rgba(var(--#{$prefix}link-color-rgb), var(--#{$prefix}link-underline-opacity, 1)),
)
)
),
"link-underline-opacity": (
css-var: true,
class: link-underline-opacity,
state: hover,
values: (
0: 0,
10: .1,
25: .25,
50: .5,
75: .75,
100: 1
),
),