bootstrap4学习总结

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    快速开始

    css

    复制粘贴样式表到head

    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css" integrity="sha384-MCw98/SFnGE8fJT3GXwEOngsV7Zt27NXFoaoApmYm81iuXoPkFOJwJ8ERdknLPMO" crossorigin="anonymous">
    integrity

    包含行内元数据，它是一个你用浏览器获取的资源文件的哈希值，以base64编码的方式加的密，这样用户能用它来验证一个获取到的资源,在传送时未被非法篡改，详情查看Subresource Integrity。

    简单说就是防止CDN篡改javascript用的

    "anonymous"会发起一个跨域请求(即包含 Origin: HTTP 头). 但不会发送任何认证信息 (即不发送 cookie, X.509 证书和 HTTP 基本认证信息). 如果服务器没有给出源站凭证 (不设置 Access-Control-Allow-Origin: HTTP 头), 这张图片就会被污染并限制使用.

    参考连接： https://imququ.com/post/subre...

    JS

    依赖jQuery，Popper.js,bootstrap自身插件

    <script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js" integrity="sha384-ZMP7rVo3mIykV+2+9J3UJ46jBk0WLaUAdn689aCwoqbBJiSnjAK/l8WvCWPIPm49" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js" integrity="sha384-ChfqqxuZUCnJSK3+MXmPNIyE6ZbWh2IMqE241rYiqJxyMiZ6OW/JmZQ5stwEULTy" crossorigin="anonymous"></script>

    顺序要一致

    注意：bootstrap.bundle.js包含了Popper，不包含jQuery

    模板

    <!doctype html>
<html lang="en">
  <head>
    <!-- Required meta tags -->
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

    <!-- Bootstrap CSS -->
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css" integrity="sha384-MCw98/SFnGE8fJT3GXwEOngsV7Zt27NXFoaoApmYm81iuXoPkFOJwJ8ERdknLPMO" crossorigin="anonymous">

    <title>Hello, world!</title>
  </head>
  <body>
    <h1>Hello, world!</h1>

    <!-- Optional JavaScript -->
    <!-- jQuery first, then Popper.js, then Bootstrap JS -->
    <script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js" integrity="sha384-ZMP7rVo3mIykV+2+9J3UJ46jBk0WLaUAdn689aCwoqbBJiSnjAK/l8WvCWPIPm49" crossorigin="anonymous"></script>
    <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js" integrity="sha384-ChfqqxuZUCnJSK3+MXmPNIyE6ZbWh2IMqE241rYiqJxyMiZ6OW/JmZQ5stwEULTy" crossorigin="anonymous"></script>
  </body>
</html>

    响应式meta标签

    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

    Box-sizing

    将属性值改为：

    {
    box-sizing: content-box ---> border-box
}

    Layout

    Containers

    源码

    .container {
  width: 100%;
  padding-right: 15px;
  padding-left: 15px;
  margin-right: auto;
  margin-left: auto;
}

    在页面中.container不是占满全屏的

    @media (min-width: 576px) {
  .container {
    max-width: 540px;
  }
}

@media (min-width: 768px) {
  .container {
    max-width: 720px;
  }
}

@media (min-width: 992px) {
  .container {
    max-width: 960px;
  }
}

@media (min-width: 1200px) {
  .container {
    max-width: 1140px;
  }
}

    媒体查询设置max-width的断点导致左右居中

    应该有计算公式，后面再说

    使用containe-fulid占满整个视窗

    Z-index

    以下组件都使用z-index

    $zindex-dropdown:          1000 !default;
$zindex-sticky:            1020 !default;
$zindex-fixed:             1030 !default;
$zindex-modal-backdrop:    1040 !default;
$zindex-modal:             1050 !default;
$zindex-popover:           1060 !default;
$zindex-tooltip:           1070 !default;

    栅格系统

    原理：基于flex布局和媒体查询

    官方代码片段

    <div class="container">
  <div class="row">
    <div class="col-sm">
      One of three columns
    </div>
    <div class="col-sm">
      One of three columns
    </div>
    <div class="col-sm">
      One of three columns
    </div>
  </div>
</div>

    先说.row

    .row {
  //
  display: -webkit-box; /* Chrome 4+, Safari 3.1, iOS Safari 3.2+ */
  display: -ms-flexbox; /* IE 10 */
  display: flex;
  -ms-flex-wrap: wrap;
  flex-wrap: wrap;
  margin-right: -15px;
  margin-left: -15px;
}

    可以看出css实现的兼容；还有margin左右各取-15px,这里我理解为拉长.row元素自身的宽度，跟.container达成一致

    再看下.col-sm

    
// 所有的columns类名的共有属性
.col-1, .col-2, .col-3, .col-4, .col-5, .col-6, .col-7, .col-8, .col-9, .col-10, .col-11, .col-12, .col,
.col-auto, .col-sm-1, .col-sm-2, .col-sm-3, .col-sm-4, .col-sm-5, .col-sm-6, .col-sm-7, .col-sm-8, .col-sm-9, .col-sm-10, .col-sm-11, .col-sm-12, .col-sm,
.col-sm-auto, .col-md-1, .col-md-2, .col-md-3, .col-md-4, .col-md-5, .col-md-6, .col-md-7, .col-md-8, .col-md-9, .col-md-10, .col-md-11, .col-md-12, .col-md,
.col-md-auto, .col-lg-1, .col-lg-2, .col-lg-3, .col-lg-4, .col-lg-5, .col-lg-6, .col-lg-7, .col-lg-8, .col-lg-9, .col-lg-10, .col-lg-11, .col-lg-12, .col-lg,
.col-lg-auto, .col-xl-1, .col-xl-2, .col-xl-3, .col-xl-4, .col-xl-5, .col-xl-6, .col-xl-7, .col-xl-8, .col-xl-9, .col-xl-10, .col-xl-11, .col-xl-12, .col-xl,
.col-xl-auto {
  position: relative;
  width: 100%;
  min-height: 1px;
  padding-right: 15px;
  padding-left: 15px;
}


@media (min-width: 576px) {

.col-sm {
    -ms-flex-preferred-size: 0;
    flex-basis: 0;
    -webkit-box-flex: 1;
    -ms-flex-positive: 1;
    flex-grow: 1;
    max-width: 100%;
  }

}

    先说第一个知识点，ming-height: 1px,这个东东有什么用的，简单的说，就是当.col-sm的元素不包含文本时，不会发生水平折叠的尴尬现象，这里我参考大佬的文章
    放心，我不写flex属性：）

    这里先说下5大layout，分别是extra small（<576px）,small（≥576px）,medium（≥768px）,large（≥992px）,extra large（≥1200px）。.col-sm适合除extra small之外的。

    .no-gutter消除columns的padding以及.row的margin

    .no-gutters {
  margin-right: 0;
  margin-left: 0;
}

.no-gutters > .col,
.no-gutters > [class*="col-"] {
  padding-right: 0;
  padding-left: 0;
}

    等宽

    .col适用于所有的layout

    .col {
  -ms-flex-preferred-size: 0;
  flex-basis: 0;
  -webkit-box-flex: 1;
  -ms-flex-positive: 1;
  flex-grow: 1;
  max-width: 100%;
}

    这里注意max-width与flex-grow的结合占满viewport！

    .w-100

    .w-100 {
  width: 100% !important;
}

    小技巧，可以强制换行

    <div class="container">
  <div class="row">
    <div class="col">Column</div>
    <div class="col">Column</div>
    <div class="w-100"></div>
    <div class="col">Column</div>
    <div class="col">Column</div>
  </div>
</div>

    适应内容的宽度

    .col-{breakpoint}-auto

    .col-md-auto {
    -webkit-box-flex: 0;
    -ms-flex: 0 0 auto;
    flex: 0 0 auto;
    width: auto;
    max-width: none;
  }

    这一column的宽度是由内容撑开！

    Alignment

    <div class="container">
  <div class="row align-items-start">
    <div class="col">
      One of three columns
    </div>
    <div class="col">
      One of three columns
    </div>
    <div class="col">
      One of three columns
    </div>
  </div>
  <div class="row align-items-center">
    <div class="col">
      One of three columns
    </div>
    <div class="col">
      One of three columns
    </div>
    <div class="col">
      One of three columns
    </div>
  </div>
  <div class="row align-items-end">
    <div class="col">
      One of three columns
    </div>
    <div class="col">
      One of three columns
    </div>
    <div class="col">
      One of three columns
    </div>
  </div>
</div>

    控制.row的位置

    //发现.align-items-stretch和.align-items-baseline文档并没有指出
.align-items-start {
  -webkit-box-align: start !important;
  -ms-flex-align: start !important;
  align-items: flex-start !important;
}

.align-items-end {
  -webkit-box-align: end !important;
  -ms-flex-align: end !important;
  align-items: flex-end !important;
}

.align-items-center {
  -webkit-box-align: center !important;
  -ms-flex-align: center !important;
  align-items: center !important;
}

.align-items-baseline {
  -webkit-box-align: baseline !important;
  -ms-flex-align: baseline !important;
  align-items: baseline !important;
}

.align-items-stretch {
  -webkit-box-align: stretch !important;
  -ms-flex-align: stretch !important;
  align-items: stretch !important;
}

    更多align-item的区别可以参考这篇文章

    以及控制align-self的类

    .align-self-auto {
  -ms-flex-item-align: auto !important;
  align-self: auto !important;
}

.align-self-start {
  -ms-flex-item-align: start !important;
  align-self: flex-start !important;
}

.align-self-end {
  -ms-flex-item-align: end !important;
  align-self: flex-end !important;
}

.align-self-center {
  -ms-flex-item-align: center !important;
  align-self: center !important;
}

.align-self-baseline {
  -ms-flex-item-align: baseline !important;
  align-self: baseline !important;
}

.align-self-stretch {
  -ms-flex-item-align: stretch !important;
  align-self: stretch !important;
}

    水平方向排列

    <div class="container">
  <div class="row justify-content-start">
    <div class="col-4">
      One of two columns
    </div>
    <div class="col-4">
      One of two columns
    </div>
  </div>
  <div class="row justify-content-center">
    <div class="col-4">
      One of two columns
    </div>
    <div class="col-4">
      One of two columns
    </div>
  </div>
  <div class="row justify-content-end">
    <div class="col-4">
      One of two columns
    </div>
    <div class="col-4">
      One of two columns
    </div>
  </div>
  <div class="row justify-content-around">
    <div class="col-4">
      One of two columns
    </div>
    <div class="col-4">
      One of two columns
    </div>
  </div>
  <div class="row justify-content-between">
    <div class="col-4">
      One of two columns
    </div>
    <div class="col-4">
      One of two columns
    </div>
  </div>
</div>

    通过控制justify-content来控制

      .justify-content-sm-start {
    -webkit-box-pack: start !important;
    -ms-flex-pack: start !important;
    justify-content: flex-start !important;
  }
  .justify-content-sm-end {
    -webkit-box-pack: end !important;
    -ms-flex-pack: end !important;
    justify-content: flex-end !important;
  }
  .justify-content-sm-center {
    -webkit-box-pack: center !important;
    -ms-flex-pack: center !important;
    justify-content: center !important;
  }
  .justify-content-sm-between {
    -webkit-box-pack: justify !important;
    -ms-flex-pack: justify !important;
    justify-content: space-between !important;
  }
  .justify-content-sm-around {
    -ms-flex-pack: distribute !important;
    justify-content: space-around !important;
  }

    通过order-*控制列的顺序

    .order-first {
  -webkit-box-ordinal-group: 0;
  -ms-flex-order: -1;
  order: -1;
}

.order-last {
  -webkit-box-ordinal-group: 14;
  -ms-flex-order: 13;
  order: 13;
}

.order-0 {
  -webkit-box-ordinal-group: 1;
  -ms-flex-order: 0;
  order: 0;
}

.order-1 {
  -webkit-box-ordinal-group: 2;
  -ms-flex-order: 1;
  order: 1;
}

.order-2 {
  -webkit-box-ordinal-group: 3;
  -ms-flex-order: 2;
  order: 2;
}

.order-3 {
  -webkit-box-ordinal-group: 4;
  -ms-flex-order: 3;
  order: 3;
}

.order-4 {
  -webkit-box-ordinal-group: 5;
  -ms-flex-order: 4;
  order: 4;
}

.order-5 {
  -webkit-box-ordinal-group: 6;
  -ms-flex-order: 5;
  order: 5;
}

.order-6 {
  -webkit-box-ordinal-group: 7;
  -ms-flex-order: 6;
  order: 6;
}

.order-7 {
  -webkit-box-ordinal-group: 8;
  -ms-flex-order: 7;
  order: 7;
}

.order-8 {
  -webkit-box-ordinal-group: 9;
  -ms-flex-order: 8;
  order: 8;
}

.order-9 {
  -webkit-box-ordinal-group: 10;
  -ms-flex-order: 9;
  order: 9;
}

.order-10 {
  -webkit-box-ordinal-group: 11;
  -ms-flex-order: 10;
  order: 10;
}

.order-11 {
  -webkit-box-ordinal-group: 12;
  -ms-flex-order: 11;
  order: 11;
}

.order-12 {
  -webkit-box-ordinal-group: 13;
  -ms-flex-order: 12;
  order: 12;
}

    偏移

    示例

    <div class="row">
  <div class="col-md-4">.col-md-4</div>
  <div class="col-md-4 offset-md-4">.col-md-4 .offset-md-4</div>
</div>
<div class="row">
  <div class="col-md-3 offset-md-3">.col-md-3 .offset-md-3</div>
  <div class="col-md-3 offset-md-3">.col-md-3 .offset-md-3</div>
</div>
<div class="row">
  <div class="col-md-6 offset-md-3">.col-md-6 .offset-md-3</div>
</div>

    都是设置margin-left的百分比控制偏移量

    .offset-md-0 {
    margin-left: 0;
  }
  .offset-md-1 {
    margin-left: 8.333333%;
  }
  .offset-md-2 {
    margin-left: 16.666667%;
  }
  .offset-md-3 {
    margin-left: 25%;
  }
  .offset-md-4 {
    margin-left: 33.333333%;
  }
  .offset-md-5 {
    margin-left: 41.666667%;
  }
  .offset-md-6 {
    margin-left: 50%;
  }
  .offset-md-7 {
    margin-left: 58.333333%;
  }
  .offset-md-8 {
    margin-left: 66.666667%;
  }
  .offset-md-9 {
    margin-left: 75%;
  }
  .offset-md-10 {
    margin-left: 83.333333%;
  }
  .offset-md-11 {
    margin-left: 91.666667%;
  }

    后面都是讲scss定制，暂时忽略

    cssbootstrap
    看见了
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