颜色
警告框
警告框（alert）组件
Well done!
警告框（alert）组件还可以包含其它 HTML 元素，例如标题、段落、分割线等。
添加图标和关闭按钮
徽章（Badge）
标题中的徽章 New
通过使用背景色（background）相关的工具类可以快速更改徽章（badge）组件的外观。请注意，使用 Bootstrap 的默认 .bg-light 类时，你需要使用文本颜色相关的工具类
（例如 .text-dark）来设置适当的文本颜色。这是因为背景色相关的工具类除了设置 background-color 外不会更改任何其它设置。
Primary Secondary Success Danger Warning Info Light Dark
胶囊式徽章（Pill badges）
使用 .rounded-pill 工具类能够让徽章（badge）组件的边角变得更圆滑（这是通过设置更大的 border-radius 实现的）。Primary Secondary Success Danger Warning Info Light Dark
按钮（Buttons）
可用作按钮的 HTML 标签
.btn 系列类（class）被设计为用于 button 元素。不过，你也可以将这些类用于 a 或 input 元素 （但是某些浏览器可能会使用略有不同的渲染方式）。Link
按钮的尺寸
需要更大或更小的按钮吗？使用 .btn-lg 或 .btn-sm 类可以设置按钮的不同尺寸带轮廓线的按钮
当你需要使用按钮，但不希望按钮带有背景颜色时，请将默认的修饰符类（modifier class） 替换为 .btn-outline-* 系列类（class），已去除按钮上的所有背景图片和颜色。
卡片（Cards）
Some quick example text to build on the card title and make up the bulk of the card's content.
- An item
- A second item
- A third item
Special title treatment
With supporting text below as a natural lead-in to additional content.
Go somewhereSpecial title treatment
With supporting text below as a natural lead-in to additional content.
Go somewherePrimary card title
Some quick example text to build on the card title and make up the bulk of the card's content.
Secondary card title
Some quick example text to build on the card title and make up the bulk of the card's content.
Success card title
Some quick example text to build on the card title and make up the bulk of the card's content.
Danger card title
Some quick example text to build on the card title and make up the bulk of the card's content.
Warning card title
Some quick example text to build on the card title and make up the bulk of the card's content.
Info card title
Some quick example text to build on the card title and make up the bulk of the card's content.
Light card title
Some quick example text to build on the card title and make up the bulk of the card's content.
Dark card title
Some quick example text to build on the card title and make up the bulk of the card's content.
Primary card title
Some quick example text to build on the card title and make up the bulk of the card's content.
Secondary card title
Some quick example text to build on the card title and make up the bulk of the card's content.
Success card title
Some quick example text to build on the card title and make up the bulk of the card's content.
Danger card title
Some quick example text to build on the card title and make up the bulk of the card's content.
Warning card title
Some quick example text to build on the card title and make up the bulk of the card's content.
Info card title
Some quick example text to build on the card title and make up the bulk of the card's content.
Light card title
Some quick example text to build on the card title and make up the bulk of the card's content.
Dark card title
Some quick example text to build on the card title and make up the bulk of the card's content.