学习 Bootstrap 打通任督二脉（三）本文旨在根据官方文档全面学习 Bootstrap. 学习其目标在于为之后使用

本文旨在根据官方文档全面学习 Bootstrap. 学习其目标在于为之后使用其他更加高级的组件库打下坚实的基础。同时由于 Bootstrap 在移动端的亮眼表现，到目前为止，已经是不可逾越的技术点，因此在本文中，让我们下定决心一起突破，拿下 Bootstrap, 打通任督二脉。

弹性盒子 -- Flex

内容的位置和方向

<div class="d-flex flex-row bd-highlight mb-3">
  <div class="p-2 bd-highlight">Flex item 1</div>
  <div class="p-2 bd-highlight">Flex item 2</div>
  <div class="p-2 bd-highlight">Flex item 3</div>
</div>
<div class="d-flex flex-row-reverse bd-highlight">
  <div class="p-2 bd-highlight">Flex item 1</div>
  <div class="p-2 bd-highlight">Flex item 2</div>
  <div class="p-2 bd-highlight">Flex item 3</div>
</div>

<div class="d-flex flex-column bd-highlight mb-3">
  <div class="p-2 bd-highlight">Flex item 1</div>
  <div class="p-2 bd-highlight">Flex item 2</div>
  <div class="p-2 bd-highlight">Flex item 3</div>
</div>
<div class="d-flex flex-column-reverse bd-highlight">
  <div class="p-2 bd-highlight">Flex item 1</div>
  <div class="p-2 bd-highlight">Flex item 2</div>
  <div class="p-2 bd-highlight">Flex item 3</div>
</div>

结合 break Points：

.flex-row
.flex-row-reverse
.flex-column
.flex-column-reverse
.flex-sm-row
.flex-sm-row-reverse
.flex-sm-column
.flex-sm-column-reverse
.flex-md-row
.flex-md-row-reverse
.flex-md-column
.flex-md-column-reverse
.flex-lg-row
.flex-lg-row-reverse
.flex-lg-column
.flex-lg-column-reverse
.flex-xl-row
.flex-xl-row-reverse
.flex-xl-column
.flex-xl-column-reverse
.flex-xxl-row
.flex-xxl-row-reverse
.flex-xxl-column
.flex-xxl-column-reverse

对内容精细调节

<div class="d-flex justify-content-start">...</div>
<div class="d-flex justify-content-end">...</div>
<div class="d-flex justify-content-center">...</div>
<div class="d-flex justify-content-between">...</div>
<div class="d-flex justify-content-around">...</div>
<div class="d-flex justify-content-evenly">...</div>

<div class="d-flex align-items-start">...</div>
<div class="d-flex align-items-end">...</div>
<div class="d-flex align-items-center">...</div>
<div class="d-flex align-items-baseline">...</div>
<div class="d-flex align-items-stretch">...</div>

以及和 break Points 的结合使用：

.justify-content-start
.justify-content-end
.justify-content-center
.justify-content-between
.justify-content-around
.justify-content-evenly
.justify-content-sm-start
.justify-content-sm-end
.justify-content-sm-center
.justify-content-sm-between
.justify-content-sm-around
.justify-content-sm-evenly
.justify-content-md-start
.justify-content-md-end
.justify-content-md-center
.justify-content-md-between
.justify-content-md-around
.justify-content-md-evenly
.justify-content-lg-start
.justify-content-lg-end
.justify-content-lg-center
.justify-content-lg-between
.justify-content-lg-around
.justify-content-lg-evenly
.justify-content-xl-start
.justify-content-xl-end
.justify-content-xl-center
.justify-content-xl-between
.justify-content-xl-around
.justify-content-xl-evenly
.justify-content-xxl-start
.justify-content-xxl-end
.justify-content-xxl-center
.justify-content-xxl-between
.justify-content-xxl-around
.justify-content-xxl-evenly
.align-items-start
.align-items-end
.align-items-center
.align-items-baseline
.align-items-stretch
.align-items-sm-start
.align-items-sm-end
.align-items-sm-center
.align-items-sm-baseline
.align-items-sm-stretch
.align-items-md-start
.align-items-md-end
.align-items-md-center
.align-items-md-baseline
.align-items-md-stretch
.align-items-lg-start
.align-items-lg-end
.align-items-lg-center
.align-items-lg-baseline
.align-items-lg-stretch
.align-items-xl-start
.align-items-xl-end
.align-items-xl-center
.align-items-xl-baseline
.align-items-xl-stretch
.align-items-xxl-start
.align-items-xxl-end
.align-items-xxl-center
.align-items-xxl-baseline
.align-items-xxl-stretch

在所在轴上排布

<div class="align-self-start">Aligned flex item</div>
<div class="align-self-end">Aligned flex item</div>
<div class="align-self-center">Aligned flex item</div>
<div class="align-self-baseline">Aligned flex item</div>
<div class="align-self-stretch">Aligned flex item</div>

和 break Points 结合使用：

.align-self-start
.align-self-end
.align-self-center
.align-self-baseline
.align-self-stretch
.align-self-sm-start
.align-self-sm-end
.align-self-sm-center
.align-self-sm-baseline
.align-self-sm-stretch
.align-self-md-start
.align-self-md-end
.align-self-md-center
.align-self-md-baseline
.align-self-md-stretch
.align-self-lg-start
.align-self-lg-end
.align-self-lg-center
.align-self-lg-baseline
.align-self-lg-stretch
.align-self-xl-start
.align-self-xl-end
.align-self-xl-center
.align-self-xl-baseline
.align-self-xl-stretch
.align-self-xxl-start
.align-self-xxl-end
.align-self-xxl-center
.align-self-xxl-baseline
.align-self-xxl-stretch

防止自动收缩

<div class="d-flex bd-highlight">
  <div class="p-2 flex-fill bd-highlight">Flex item with a lot of content</div>
  <div class="p-2 flex-fill bd-highlight">Flex item</div>
  <div class="p-2 flex-fill bd-highlight">Flex item</div>
</div>

.flex-fill {
  flex: 1 1 auto !important;
}

以及和 break Points 的结合使用：

.flex-fill
.flex-sm-fill
.flex-md-fill
.flex-lg-fill
.flex-xl-fill
.flex-xxl-fill

小战一下

布局左1 左2 右1:

先看一下比较传统的做法：

使用 ms-auto

.ms-auto {
  margin-left: auto !important;
}

.me-auto {
  margin-right: auto !important;
}

扩展一下：

使用 mx-auto 快速居中

同理，在 y 方向上也是一样的！

<div class="d-flex bd-highlight mb-3">
  <div class="p-2 bd-highlight">Flex item</div>
  <div class="p-2 bd-highlight">Flex item</div>
  <div class="p-2 bd-highlight">Flex item</div>
</div>

<div class="d-flex bd-highlight mb-3">
  <div class="me-auto p-2 bd-highlight">Flex item</div>
  <div class="p-2 bd-highlight">Flex item</div>
  <div class="p-2 bd-highlight">Flex item</div>
</div>

<div class="d-flex bd-highlight mb-3">
  <div class="p-2 bd-highlight">Flex item</div>
  <div class="p-2 bd-highlight">Flex item</div>
  <div class="ms-auto p-2 bd-highlight">Flex item</div>
</div>

<div class="d-flex align-items-start flex-column bd-highlight mb-3" style="height: 200px;">
  <div class="mb-auto p-2 bd-highlight">Flex item</div>
  <div class="p-2 bd-highlight">Flex item</div>
  <div class="p-2 bd-highlight">Flex item</div>
</div>

<div class="d-flex align-items-end flex-column bd-highlight mb-3" style="height: 200px;">
  <div class="p-2 bd-highlight">Flex item</div>
  <div class="p-2 bd-highlight">Flex item</div>
  <div class="mt-auto p-2 bd-highlight">Flex item</div>
</div>

wrap -- 换行，不换行或者怎么换行

.flex-nowrap 不换行
.flex-wrap 换行
.flex-wrap-reverse 从下向上或者从右向左

其它相关类名：

.flex-nowrap
.flex-wrap
.flex-wrap-reverse
.flex-sm-nowrap
.flex-sm-wrap
.flex-sm-wrap-reverse
.flex-md-nowrap
.flex-md-wrap
.flex-md-wrap-reverse
.flex-lg-nowrap
.flex-lg-wrap
.flex-lg-wrap-reverse
.flex-xl-nowrap
.flex-xl-wrap
.flex-xl-wrap-reverse
.flex-xxl-nowrap
.flex-xxl-wrap
.flex-xxl-wrap-reverse

order -- 顺序

关于 order 其作用自不必多说。下面看看其可用的种类都有哪些？

<div class="d-flex flex-nowrap bd-highlight">
  <div class="order-3 p-2 bd-highlight">First flex item</div>
  <div class="order-2 p-2 bd-highlight">Second flex item</div>
  <div class="order-1 p-2 bd-highlight">Third flex item</div>
</div>

.order-0
.order-1
.order-2
.order-3
.order-4
.order-5
.order-sm-0
.order-sm-1
.order-sm-2
.order-sm-3
.order-sm-4
.order-sm-5
.order-md-0
.order-md-1
.order-md-2
.order-md-3
.order-md-4
.order-md-5
.order-lg-0
.order-lg-1
.order-lg-2
.order-lg-3
.order-lg-4
.order-lg-5
.order-xl-0
.order-xl-1
.order-xl-2
.order-xl-3
.order-xl-4
.order-xl-5
.order-xxl-0
.order-xxl-1
.order-xxl-2
.order-xxl-3
.order-xxl-4
.order-xxl-5
.order-first
.order-last
.order-sm-first
.order-sm-last
.order-md-first
.order-md-last
.order-lg-first
.order-lg-last
.order-xl-first
.order-xl-last
.order-xxl-first
.order-xxl-last

阴影

关于阴影，我们有默认值并且我觉得这就足够了。使用起来也是相当方便的！

<div class="shadow-none p-3 mb-5 bg-light rounded">No shadow</div>
<div class="shadow-sm p-3 mb-5 bg-body rounded">Small shadow</div>
<div class="shadow p-3 mb-5 bg-body rounded">Regular shadow</div>
<div class="shadow-lg p-3 mb-5 bg-body rounded">Larger shadow</div>

$box-shadow:                  0 .5rem 1rem rgba($black, .15);
$box-shadow-sm:               0 .125rem .25rem rgba($black, .075);
$box-shadow-lg:               0 1rem 3rem rgba($black, .175);
$box-shadow-inset:            inset 0 1px 2px rgba($black, .075);

子元素宽度、高度

使用 w-* 设置静态布局的子元素相对于父元素的宽度。

<div class="w-25 p-3" style="background-color: #eee;">Width 25%</div>
<div class="w-50 p-3" style="background-color: #eee;">Width 50%</div>
<div class="w-75 p-3" style="background-color: #eee;">Width 75%</div>
<div class="w-100 p-3" style="background-color: #eee;">Width 100%</div>
<div class="w-auto p-3" style="background-color: #eee;">Width auto</div>

使用 h-* 设置静态布局的子元素相对于父元素的宽度。

<div style="height: 100px; background-color: rgba(255,0,0,0.1);">
  <div class="h-25 d-inline-block" style="width: 120px; background-color: rgba(0,0,255,.1)">Height 25%</div>
  <div class="h-50 d-inline-block" style="width: 120px; background-color: rgba(0,0,255,.1)">Height 50%</div>
  <div class="h-75 d-inline-block" style="width: 120px; background-color: rgba(0,0,255,.1)">Height 75%</div>
  <div class="h-100 d-inline-block" style="width: 120px; background-color: rgba(0,0,255,.1)">Height 100%</div>
  <div class="h-auto d-inline-block" style="width: 120px; background-color: rgba(0,0,255,.1)">Height auto</div>
</div>

好一点的布局都是 width 和 max-width 结合使用的！ mw-100 mh-100 这里的 100 指的是 100% 而不是 100px

<img src="..." class="mw-100" alt="...">

<div style="height: 100px; background-color: rgba(255,0,0,.1);">
  <div class="mh-100" style="width: 100px; height: 200px; background-color: rgba(0,0,255,.1);">Max-height 100%</div>
</div>

相对于窗口： 使用的是 vh 和 vw

<div class="min-vw-100">Min-width 100vw</div>
<div class="min-vh-100">Min-height 100vh</div>
<div class="vw-100">Width 100vw</div>
<div class="vh-100">Height 100vh</div>

spacing

和 spacing 相关的类被整理然后统一罗列了出来，它们是：

m - for classes that set margin
p - for classes that set padding
t - for classes that set margin-top or padding-top
b - for classes that set margin-bottom or padding-bottom
s - (start) for classes that set margin-left or padding-left in LTR, margin-right or padding-right in RTL
e - (end) for classes that set margin-right or padding-right in LTR, margin-left or padding-left in RTL
x - for classes that set both *-left and *-right
y - for classes that set both *-top and *-bottom
blank - for classes that set a margin or padding on all 4 sides of the element
0 - for classes that eliminate the margin or padding by setting it to 0
1 - (by default) for classes that set the margin or padding to $spacer * .25
2 - (by default) for classes that set the margin or padding to $spacer * .5
3 - (by default) for classes that set the margin or padding to $spacer
4 - (by default) for classes that set the margin or padding to $spacer * 1.5
5 - (by default) for classes that set the margin or padding to $spacer * 3
auto - for classes that set the margin to auto

关于负的距离如下所示：

.mt-n1 {
  margin-top: -0.25rem !important;
}

居中的写法：

<div class="mx-auto" style="width: 200px;">
  Centered element
</div>

grid 布局中的 gap:

<div class="d-grid gap-3">
  <div class="p-2 bg-light border">Grid item 1</div>
  <div class="p-2 bg-light border">Grid item 2</div>
  <div class="p-2 bg-light border">Grid item 3</div>
</div>

效果嘎嘎好

其中，

.gap-3 {
  gap: 1rem !important;
}

文字

文字的左中右和 break points:

<p class="text-start">Start aligned text on all viewport sizes.</p>
<p class="text-center">Center aligned text on all viewport sizes.</p>
<p class="text-end">End aligned text on all viewport sizes.</p>

<p class="text-sm-start">Start aligned text on viewports sized SM (small) or wider.</p>
<p class="text-md-start">Start aligned text on viewports sized MD (medium) or wider.</p>
<p class="text-lg-start">Start aligned text on viewports sized LG (large) or wider.</p>
<p class="text-xl-start">Start aligned text on viewports sized XL (extra-large) or wider.</p>

单词空白处换行和不换行

<div class="badge bg-primary text-wrap" style="width: 6rem;">
  This text should wrap.
</div>

<div class="text-nowrap bd-highlight" style="width: 8rem;">
  This text should overflow the parent.
</div>

使用 text-break 可以强制在一个单词中间换行：

<p class="text-break">mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm</p>

使用相关类名甚至可以控制文本的大小写：

<p class="text-lowercase">Lowercased text.</p>
<p class="text-uppercase">Uppercased text.</p>
<p class="text-capitalize">CapiTaliZed text.</p>

使用类名可以快速创建出和 h1-h6 相同大小的字来：

<p class="fs-1">.fs-1 text</p>
<p class="fs-2">.fs-2 text</p>
<p class="fs-3">.fs-3 text</p>
<p class="fs-4">.fs-4 text</p>
<p class="fs-5">.fs-5 text</p>
<p class="fs-6">.fs-6 text</p>

关于字重和倾斜：

<p class="fw-bold">Bold text.</p>
<p class="fw-bolder">Bolder weight text (relative to the parent element).</p>
<p class="fw-normal">Normal weight text.</p>
<p class="fw-light">Light weight text.</p>
<p class="fw-lighter">Lighter weight text (relative to the parent element).</p>
<p class="fst-italic">Italic text.</p>
<p class="fst-normal">Text with normal font style</p>

关于段落高度：

<p class="lh-1">This is a long paragraph written to show how the line-height of an element is affected by our utilities. Classes are applied to the element itself or sometimes the parent element. These classes can be customized as needed with our utility API.</p>
<p class="lh-sm">This is a long paragraph written to show how the line-height of an element is affected by our utilities. Classes are applied to the element itself or sometimes the parent element. These classes can be customized as needed with our utility API.</p>
<p class="lh-base">This is a long paragraph written to show how the line-height of an element is affected by our utilities. Classes are applied to the element itself or sometimes the parent element. These classes can be customized as needed with our utility API.</p>
<p class="lh-lg">This is a long paragraph written to show how the line-height of an element is affected by our utilities. Classes are applied to the element itself or sometimes the parent element. These classes can be customized as needed with our utility API.</p>

monospace 字体的使用：

<p class="font-monospace">This is in monospace</p>

字体颜色继承： 使用 teext-reset 完成字体颜色的继承，特别适用于一段文字中插入一个 a 标签这种。

<p class="text-muted">
  Muted text with a <a href="#" class="text-reset">reset link</a>.
</p>

对比默认情况下：

原理：

.text-reset {
    --bs-text-opacity: 1;
    color: inherit !important;
}

文字的装饰，如下划线等：

<p class="text-decoration-underline">This text has a line underneath it.</p>
<p class="text-decoration-line-through">This text has a line going through it.</p>
<a href="#" class="text-decoration-none">This link has its text decoration removed</a>