Bootstrap 如何在面包屑组件中添加“/”？

Question

v3 和 v4 中的 Bootstrap 面包屑组件都添加了一个“/”来列出项目：

http://getbootstrap.com/components/#breadcrumbs

https://v4-alpha.getbootstrap.com/components/breadcrumb/

文档说：

分隔符通过 ::before 和 content 自动添加到 CSS 中。

所以，我查看了源代码，相关部分显示：

.breadcrumb-item + .breadcrumb-item::before {
  display: inline-block;
  padding-right: 0.5rem;
  padding-left: 0.5rem;
  color: #636c72;
  content: "/";
}

然而，content: "/";唯一存在的breadcrumb-item规则。然而，当我遵循 v3 文档时它似乎工作，它不需要breadcrumb-item列表中项目的类：

<ol class="breadcrumb">
  <li class=''><a href="#">Home</a></li>
  <li class=''><a href="#">Library</a></li>
  <li class="active">Data</li>
</ol>

JSFiddle

为什么带有上述 CSS 的上述 HTML 导致/分隔符被添加到.breadcrumb列表中的项目，即使它们没有.breadcrumb-item类，因此无法从content: "/"规则中受益？检查 JSFiddle 中的输出 HTML 表明没有引导 javascript 魔术.breadcrumb-item向我的 html 列表项添加了一个类。

Answer 1

链接到 github 上的此样式（bootstrap v3.3.7）：

https://github.com/twbs/bootstrap/blob/v3.3.7/less/breadcrumbs.less

对于（引导程序 v4.0.0）：

https://github.com/twbs/bootstrap/blob/v4.0.0-alpha.6/scss/_breadcrumb.scss

(bootstrap v3.3.7 --> breadcrumbs.less)

//
// Breadcrumbs
// --------------------------------------------------


.breadcrumb {
  padding: @breadcrumb-padding-vertical @breadcrumb-padding-horizontal;
  margin-bottom: @line-height-computed;
  list-style: none;
  background-color: @breadcrumb-bg;
  border-radius: @border-radius-base;

  > li {
    display: inline-block;

    + li:before {
      content: "@{breadcrumb-separator}\00a0"; // Unicode space added since inline-block means non-collapsing white-space
      padding: 0 5px;
      color: @breadcrumb-color;
    }
  }

  > .active {
    color: @breadcrumb-active-color;
  }
}

（引导程序 v4.0.0 --> _breadcrumb.scss）

.breadcrumb {
  padding: $breadcrumb-padding-y $breadcrumb-padding-x;
  margin-bottom: $spacer-y;
  list-style: none;
  background-color: $breadcrumb-bg;
  @include border-radius($border-radius);
  @include clearfix;
}

.breadcrumb-item {
  float: left;

  // The separator between breadcrumbs (by default, a forward-slash: "/")
  + .breadcrumb-item::before {
    display: inline-block; // Suppress underlining of the separator in modern browsers
    padding-right: $breadcrumb-item-padding;
    padding-left: $breadcrumb-item-padding;
    color: $breadcrumb-divider-color;
    content: "#{$breadcrumb-divider}";
  }

  // IE9-11 hack to properly handle hyperlink underlines for breadcrumbs built
  // without `<ul>`s. The `::before` pseudo-element generates an element
  // *within* the .breadcrumb-item and thereby inherits the `text-decoration`.
  //
  // To trick IE into suppressing the underline, we give the pseudo-element an
  // underline and then immediately remove it.
  + .breadcrumb-item:hover::before {
    text-decoration: underline;
  }
  + .breadcrumb-item:hover::before {
    text-decoration: none;
  }

  &.active {
    color: $breadcrumb-active-color;
  }
}