Bootstrap多级下拉菜单超出屏幕右侧问题求助

当前实现仅处理了一级下拉菜单的对齐逻辑，内层子菜单未做屏幕边界检测，导致空间不足时会超出屏幕右侧。以下是优化后的完整解决方案：

修改后的完整代码 #

HTML #

<!DOCTYPE html>
<html lang="zh-CN">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Dropdown Menu Alignment</title>
  <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.3/dist/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-QWTKZyjpPEjISv5WaRU9OFeRpok6YctnYmDr5pNlyT2bRjXh0JMhjY6hW+ALEwIH" crossorigin="anonymous">
  <style>
    /* 自定义CSS */
    body {
      font-family: Verdana, Geneva, Tahoma, sans-serif;
    }

    .navbar {
      display: flex;
      flex-direction: column;
      justify-content: space-between;
      align-items: center;
      padding: 10px;
      background-color: dimgrey;
      width: 100%;
    }

    .navbar-top {
      display: flex;
      justify-content: space-between;
      width: 100%;
      align-items: center;
    }

    .navbar-left {
      display: flex;
      align-items: center;
    }

    .navbar-brand {
      margin-right: 20px;
    }

    .switch-role-form {
      display: flex;
      align-items: center;
    }

    .switch-role {
      margin-right: 10px;
    }

    .welcome-message {
      color: blue;
      text-align: right;
    }

    .logout-button {
      top: 10px;
      right: 10px;
    }

    .navbar-nav {
      display: flex;
      justify-content: center;
      width: 100%;
      background-color: palevioletred;
    }

    .dropdown-menu li {
      position: relative;
    }

    /* 默认子菜单向右展开 */
    .dropdown-menu .dropdown-submenu {
      display: none;
      position: absolute;
      left: 100%;
      top: -7px;
    }

    /* 子菜单向左展开的类 */
    .dropdown-submenu-left {
      right: 100%;
      left: auto;
    }

    .dropdown-menu>li:hover>.dropdown-submenu {
      display: block;
    }

    .nav-item:hover>.dropdown-menu {
      display: block;
    }

    .dropdown-submenu:hover>.dropdown-menu {
      display: block;
    }

    .navbar-expand-lg {
      width: 100%;
      display: flex;
      justify-content: center;
    }

    /* 一级下拉菜单右对齐类 */
    .dropdown-menu-end {
      left: auto;
      right: 0;
    }
  </style>
</head>
<body>
  <div class="navbar">
    <nav class="navbar navbar-expand-lg bg-body-tertiary">
      <div class="container-fluid">
        <ul class="navbar-nav">
          <li class="nav-item dropdown">
            <a class="nav-link dropdown-toggle" href="#" role="button" data-bs-toggle="dropdown" aria-expanded="false">
              Menu Item
            </a>
            <ul class="dropdown-menu dropdown-menu-end"> <!-- 默认右对齐 -->
              <li>
                <a class="dropdown-item" href="#">Submenu Item »</a>
                <ul class="dropdown-menu dropdown-submenu">
                  <li><a class="dropdown-item" href="#">Submenu Item 1</a></li>
                  <li><a class="dropdown-item" href="#">Submenu Item 2</a></li>
                </ul>
              </li>
              <li><a class="dropdown-item" href="#">Another Item</a></li>
            </ul>
          </li>
        </ul>
      </div>
    </nav>
  </div>

  <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.7.1/jquery.min.js"></script>
  <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0-alpha1/dist/js/bootstrap.bundle.min.js"></script>
  <script>
    // 动态调整下拉菜单对齐的函数
    function adjustDropdownAlignment() {
      $('.dropdown-menu').each(function() {
        var $menu = $(this);
        var rect = $menu[0].getBoundingClientRect();
        
        // 处理一级下拉菜单
        if ($menu.hasClass('dropdown-menu-end')) {
          if (rect.right > window.innerWidth) {
            $menu.removeClass('dropdown-menu-end');
          } else {
            $menu.addClass('dropdown-menu-end');
          }
        }
        
        // 处理子菜单
        if ($menu.hasClass('dropdown-submenu')) {
          if (rect.right > window.innerWidth) {
            $menu.addClass('dropdown-submenu-left');
          } else {
            $menu.removeClass('dropdown-submenu-left');
          }
        }
      });
    }

    $(document).ready(function() {
      // 鼠标悬停时触发调整
      $('.nav-item.dropdown, .dropdown-submenu').on('mouseenter', adjustDropdownAlignment);
      
      // 窗口大小变化时重新调整
      $(window).on('resize', adjustDropdownAlignment);
    });
  </script>
</body>
</html>

关键修改说明 #

• 默认对齐设置：给一级下拉菜单默认添加dropdown-menu-end类，实现初始右对齐
• 全层级检测：遍历所有下拉菜单（包括子菜单），分别处理一级菜单和子菜单的边界检测逻辑
• 响应窗口变化：添加窗口resize事件监听，确保窗口大小改变时重新计算菜单位置
• 子菜单切换逻辑：当子菜单右侧超出屏幕时，添加dropdown-submenu-left类切换为向左展开

内容的提问来源于stack exchange，提问作者Yuvraj Jadhav