Bootstrap下拉子菜单关闭上游子菜单

<nav class="navbar">
  <ul class="navbar-nav">
    <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">
        父级菜单
      </a>
      <div class="dropdown-menu" aria-labelledby="navbarDropdown">
        <a class="dropdown-item" href="#">子菜单1</a>
        <a class="dropdown-item" href="#">子菜单2</a>
        <div class="dropdown-divider"></div>
        <a class="dropdown-item" href="#">子菜单3</a>
      </div>
    </li>
  </ul>
</nav>

<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/css/bootstrap.min.css">
<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/js/bootstrap.min.js"></script>

document.querySelector('.dropdown-toggle').addEventListener('click', function() {
  var dropdownMenu = this.nextElementSibling;
  if (dropdownMenu.style.display === 'none') {
    dropdownMenu.style.display = 'block';
  } else {
    dropdownMenu.style.display = 'none';
  }
});