如何修复不起作用的折叠（使用 Bootstrap 4.0.0）？

Question

这是我的代码

    <ul class="list-unstyled components">
                    <p>Menus</p>
                    <li>
                        <a href="#employeeform" data-toggle="collapse" data-target="#employeeform" aria-expanded="false" class="dropdown-toggle">Employee</a>
                        <ul class="collapse" id="employeeform">
                            <li>
                                <a href="#">Add New Employee</a>
                            </li>
                            <li>
                                <a href="#">Edit Employee's Data</a>
                            </li>
                        </ul>
                    </li>

                    <li>
                        <a href="#customerform" data-toggle="collapse" data-target="#customerform" aria-expanded="false" class="dropdown-toggle">Customer</a>
                        <ul class="collapse list-unstyled" id="customerform">
                            <li>
                                <a href="#">Add New Customer</a>
                            </li>
                            <li>
                                <a href="#">Edit Customer's Data</a>
                            </li>
                        </ul>
                    </li>
</ul>

问题是，每当我单击 a 元素（员工和客户）时，它无法进行下拉...这是我使用的脚本：

    <!-- bootdtrap css cdn -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css">

<!-- bootstrap js -->
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"></script>

<!-- popper.js -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js"></script>

<!-- ajax -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<!-- fontawesome -->
<script src="https://use.fontawesome.com/releases/v5.0.8/js/all.js"></script>

我不知道哪里出错了，非常感谢任何帮助！

Answer 1

<div class="dropdown show">
  <a class="btn btn-secondary dropdown-toggle" href="#" role="button" id="dropdownMenuLink" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
    Dropdown link
  </a>

  <div class="dropdown-menu" aria-labelledby="dropdownMenuLink">
    <a class="dropdown-item" href="#">Action</a>
    <a class="dropdown-item" href="#">Another action</a>
    <a class="dropdown-item" href="#">Something else here</a>
  </div>
</div>

Answer 2

将bootstrap.min.js放在最后。

<!-- bootdtrap css cdn -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css">

<!-- popper.js -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js"></script>

<!-- ajax -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<!-- fontawesome -->
<script src="https://use.fontawesome.com/releases/v5.0.8/js/all.js"></script>

<!-- bootstrap js -->
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.0/js/bootstrap.min.js"></script>

Answer 3

<p>
  <a class="btn btn-primary" data-toggle="collapse" href="#multiCollapseExample1" role="button" aria-expanded="false" aria-controls="multiCollapseExample1">Toggle first element</a>
  <button class="btn btn-primary" type="button" data-toggle="collapse" data-target="#multiCollapseExample2" aria-expanded="false" aria-controls="multiCollapseExample2">Toggle second element</button>
  <button class="btn btn-primary" type="button" data-toggle="collapse" data-target=".multi-collapse" aria-expanded="false" aria-controls="multiCollapseExample1 multiCollapseExample2">Toggle both elements</button>
</p>
<div class="row">
  <div class="col">
    <div class="collapse multi-collapse" id="multiCollapseExample1">
      <div class="card card-body">
        Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident.
      </div>
    </div>
  </div>
  <div class="col">
    <div class="collapse multi-collapse" id="multiCollapseExample2">
      <div class="card card-body">
        Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident.
      </div>
    </div>
  </div>
</div>

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