Bootstrap 4嵌套下拉菜单？答案

【问题标题】：Bootstrap 4 nested dropdown?Bootstrap 4嵌套下拉菜单？
【发布时间】：2019-01-23 02:38:59
【问题描述】：

我想要做的是，如果有人点击艺术，那么历史社会学和地理子菜单应该会出现。现在应该会在有人点击 Arts 时出现。
https://jsfiddle.net/0e7jdfza/

我尝试添加此代码 https://jsfiddle.net/w3zyLmgb/ 来代替艺术 li 和 ul，但它在下拉菜单中工作，尽管它在此下拉菜单之外工作

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

                <title>Hello, world!</title>
              </head>
              <body>        
    <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">
                    Select Streams
                  </a>
                  <ul class="dropdown-menu" aria-labelledby="dropdownMenuLink">
                    <li><a class="dropdown-item" href="#">Science</a></li>
                    <li><a class="dropdown-item" href="#">Commerce</a></li>
                    <li class="nav-item dropdown"><a class="dropdown-item" href="#">Arts</a>
                      <ul>
                        <li>History</li>
                        <li>Sociology</li>
                        <li>Geogrphy</li>
                      </ul>
                    </li>
                </ul>
                 </div>


            <!-- Optional JavaScript -->
            <!-- jQuery first, then Popper.js, then Bootstrap JS -->
            <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>
          </body>
        </html>

【问题讨论】：

标签： bootstrap-4

【解决方案1】：

我认为this 有点像您正在寻找的东西。

您的更新代码与其中给出的建议之一看起来与给出的示例类似。

（如果你使用 Angular，你可以使用 ngx-dropdowns 他们有嵌套下拉菜单的解决方案）

$('.dropdown-menu a.dropdown-toggle').on('click', function(e) {
  if (!$(this).next().hasClass('show')) {
    $(this).parents('.dropdown-menu').first().find('.show').removeClass("show");
  }
  var $subMenu = $(this).next(".dropdown-menu");
  $subMenu.toggleClass('show');


  $(this).parents('li.nav-item.dropdown.show').on('hidden.bs.dropdown', function(e) {
    $('.dropdown-submenu .show').removeClass("show");
  });


  return false;
});

.dropdown-submenu {
  position: relative;
}

.dropdown-submenu a::after {
  transform: rotate(-90deg);
  position: absolute;
  right: 6px;
  top: .8em;
}

.dropdown-submenu .dropdown-menu {
  top: 0;
  left: 100%;
  margin-left: .1rem;
  margin-right: .1rem;
}

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

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

<body>
  <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">
                    Select Streams
                  </a>
    <ul class="dropdown-menu" aria-labelledby="dropdownMenuLink">
      <li><a class="dropdown-item" href="#">Science</a></li>
      <li><a class="dropdown-item" href="#">Commerce</a></li>
      <li class="dropdown-submenu"><a class="dropdown-item dropdown-toggle" href="#">Arts</a>
        <ul class="dropdown-menu">
          <li><a class="dropdown-item" href="#">History</a></li>
          <li><a class="dropdown-item" href="#">Geography</a></li>
          <li><a class="dropdown-item" href="#">Sociology</a></li>

        </ul>
      </li>
    </ul>
  </div>


  <!-- Optional JavaScript -->
  <!-- jQuery first, then Popper.js, then Bootstrap JS -->
  <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>
</body>

</html>

【讨论】：

到dropleft，将css代码中的left:100%修改为right:100%

【解决方案2】：

在下面的代码中，我使用 Django 模板 for loop 循环多个下拉数据。此代码生成 2 级下拉菜单，左侧第二级下拉：

<li class="nav-item dropdown ">
    <a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown"
       aria-haspopup="true" aria-expanded="false">
        Dropdown
    </a>
    <ul class="dropdown-menu " aria-labelledby="navbarDropdown">
        {% for campus in object_list %}
            <li class="dropdown-submenu dropleft">
                <a class="dropdown-item dropdown-toggle " href="#">{{ campus.name }}</a>
                <ul class="dropdown-menu ">
                    {% for school in campus.school.all %}
                        <li><a class="dropdown-item"
                               href="">{{ school.name }}</a>
                        </li>
                    {% endfor %}
                </ul>
            </li>
        {% endfor %}
    </ul>
</li>

【讨论】：

【解决方案3】：

$(document).ready(function () {
    $("#type").change(function () {
        var val = $(this).val();
        if (val == "arts") {
            $("#type").html("<option value='history'>history</option><option value='sociology'>sociology</option><option value='geography'>geography</option>");
        } else if (val == "science") {
            $("#type").html("<option value='maths'>maths</option><option value='physics'>physics</option>");
        }
    });
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<select id="type" class="dropdown-menu" aria-labelledby="dropdownMenuLink">
    <option value="na">--Select an Item--</option>
    <option value="arts">Arts</option>
    <option value="science">Science</option>
</select>

【讨论】：