无法让引导下拉菜单正常工作

Question

我正在为我的引导程序 4.0.0 链接使用以下链接：

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">

但是，当我尝试实现基本菜单时，标准链接有效，但是如果我尝试单击Dropdown link菜单，它似乎没有任何作用。我希望如果我单击它，它会下降。

<nav class="navbar navbar-expand-sm bg-dark navbar-dark">
<ul class="navbar-nav">
<li class="nav-item"><a href="/">Home</a></li>
<li class="nav-item"><a href="/link 1">Link 1</a></li>
<li class="nav-item"><a href="/link 2">Link 2</a></li>
<li class="nav-item"><a href="/link 3">Link 3</a></li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbardrop" data-toggle="dropdown">Dropdown link</a>
<div class="dropdown-menu">
<a class="dropdown-item" href="#">link 4</a>
<a class="dropdown-item" href="#">link 5</a>
<a class="dropdown-item" href="#">link 6</a>
</div>
</li>
</ul>
</nav>

我做错了什么，为什么菜单没有打开以显示链接 4、5 和 6？

Answer 1

你只包含了 CSS for Bootstrap。您需要包含 Bootstrap 的JavaScript才能使下拉列表正常工作。在引用 Bootstrap 的 JavaScript之前，您还需要包含对两个依赖项 jQuery 和 PopperJS 的引用：

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>

这是一个添加了这些的工作示例：

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
<nav class="navbar navbar-expand-sm bg-dark navbar-dark">
<ul class="navbar-nav">
<li class="nav-item"><a href="/">Home</a></li>
<li class="nav-item"><a href="/link 1">Link 1</a></li>
<li class="nav-item"><a href="/link 2">Link 2</a></li>
<li class="nav-item"><a href="/link 3">Link 3</a></li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbardrop" data-toggle="dropdown">Dropdown link</a>
<div class="dropdown-menu">
<a class="dropdown-item" href="#">link 4</a>
<a class="dropdown-item" href="#">link 5</a>
<a class="dropdown-item" href="#">link 6</a>
</div>
</li>
</ul>
</nav>