滚动间谍

根据滚动位置自动更新 Bootstrap 导航或列表组组件，以指示哪个链接当前在视口中处于活动状态。

怎么运行的

🌐 How it works

Scrollspy 会在锚点 (<a>) 元素上切换 .active 类，当锚点的 href 引用的 id 元素滚动到可视区域时。Scrollspy 最适合与 Bootstrap 导航组件或列表组一起使用，但它也适用于当前页面的任何锚点元素。其工作原理如下。

🌐 Scrollspy toggles the .active class on anchor (<a>) elements when the element with the id referenced by the anchor’s href is scrolled into view. Scrollspy is best used in conjunction with a Bootstrap nav component or list group, but it will also work with any anchor elements in the current page. Here’s how it works.

首先，scrollspy 需要两样东西：导航、列表组或一组简单的链接，以及一个可滚动的容器。可滚动的容器可以是 <body> 或具有设定了 height 和 overflow-y: scroll 的自定义元素。
在可滚动容器上，添加 data-bs-spy="scroll" 和 data-bs-target="#navId"，其中 navId 是关联导航的唯一 id。如果元素内部没有可聚焦的元素，请务必也包含一个 tabindex="0" 以确保键盘访问。
当你滚动“被监视的”容器时，会在关联导航中的锚链接上添加和移除 .active 类。链接必须有可解析的 id 目标，否则将被忽略。例如，<a href="#home">home</a> 必须对应 DOM 中的某些内容，如 <div id="home"></div>
不会显示的目标元素将被忽略。请参阅下面的不可见元素部分。

示例

🌐 Examples

导航栏

🌐 Navbar

向下滚动导航栏下方的区域，观察 active 类的变化。打开下拉菜单，观察下拉项目也被高亮显示。

🌐 Scroll the area below the navbar and watch the active class change. Open the dropdown menu and watch the dropdown items be highlighted as well.

First heading

This is some placeholder content for the scrollspy page. Note that as you scroll down the page, the appropriate navigation link is highlighted. It’s repeated throughout the component example. We keep adding some more example copy here to emphasize the scrolling and highlighting.

Second heading

Third heading

Fourth heading

Fifth heading

<nav id="navbar-example2" class="navbar bg-body-tertiary px-3 mb-3">
  <a class="navbar-brand" href="#">Navbar</a>
  <ul class="nav nav-pills">
    <li class="nav-item">
      <a class="nav-link" href="#scrollspyHeading1">First</a>
    </li>
    <li class="nav-item">
      <a class="nav-link" href="#scrollspyHeading2">Second</a>
    </li>
    <li class="nav-item dropdown">
      <a class="nav-link dropdown-toggle" href="#" role="button" data-bs-toggle="dropdown" aria-expanded="false">Dropdown</a>
      <ul class="dropdown-menu">
        <li><a class="dropdown-item" href="#scrollspyHeading3">Third</a></li>
        <li><a class="dropdown-item" href="#scrollspyHeading4">Fourth</a></li>
        <li><hr class="dropdown-divider"></li>
        <li><a class="dropdown-item" href="#scrollspyHeading5">Fifth</a></li>
      </ul>
    </li>
  </ul>
</nav>
<div data-bs-spy="scroll" data-bs-target="#navbar-example2" data-bs-root-margin="0px 0px -40%" data-bs-smooth-scroll="true" class="scrollspy-example bg-body-tertiary p-3 rounded-2" tabindex="0">
  <h4 id="scrollspyHeading1">First heading</h4>
  <p>...</p>
  <h4 id="scrollspyHeading2">Second heading</h4>
  <p>...</p>
  <h4 id="scrollspyHeading3">Third heading</h4>
  <p>...</p>
  <h4 id="scrollspyHeading4">Fourth heading</h4>
  <p>...</p>
  <h4 id="scrollspyHeading5">Fifth heading</h4>
  <p>...</p>
</div>

嵌套导航

🌐 Nested nav

Scrollspy 同样适用于嵌套的 .nav。如果嵌套的 .nav 是 .active，它的父元素也会是 .active。滚动导航栏旁的区域，观察活动类的变化。

🌐 Scrollspy also works with nested .navs. If a nested .nav is .active, its parents will also be .active. Scroll the area next to the navbar and watch the active class change.