导航栏:如何避免在折叠时堆叠菜单项？

@media screen and (max-width: 768px) {
  .navbar {
    /* 设置导航栏为垂直布局 */
    flex-direction: column;
  }
  .navbar-item {
    /* 设置导航栏菜单项为水平布局 */
    flex-direction: row;
  }
}

<!-- 使用Bootstrap的Collapse组件 -->
<div class="navbar">
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  </button>
  <div class="collapse navbar-collapse" id="navbarNav">
    <ul class="navbar-nav">
      <li class="nav-item">
        <a class="nav-link" href="#">菜单项1</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">菜单项2</a>
      </li>
      <!-- 其他菜单项 -->
    </ul>
  </div>
</div>

@media screen and (max-width: 768px) {
  .navbar-item {
    /* 隐藏导航栏菜单项 */
    display: none;
  }
}