如何在创建可折叠菜单和子菜单时固定间距

<ul class="menu">
  <li class="menu-item">菜单项1
    <ul class="submenu">
      <li class="submenu-item">子菜单项1</li>
      <li class="submenu-item">子菜单项2</li>
      <li class="submenu-item">子菜单项3</li>
    </ul>
  </li>
  <li class="menu-item">菜单项2
    <ul class="submenu">
      <li class="submenu-item">子菜单项1</li>
      <li class="submenu-item">子菜单项2</li>
      <li class="submenu-item">子菜单项3</li>
    </ul>
  </li>
  <li class="menu-item">菜单项3</li>
</ul>

.menu {
  list-style-type: none;
  padding: 0;
}

.menu-item {
  background-color: #f0f0f0;
  padding: 10px;
  margin-bottom: 10px;
}

.submenu {
  display: none;
  list-style-type: none;
  padding: 0;
}

.submenu-item {
  background-color: #e0e0e0;
  padding: 10px;
  margin-bottom: 5px;
}

const menuItems = document.querySelectorAll('.menu-item');

menuItems.forEach(item => {
  item.addEventListener('click', () => {
    const submenu = item.querySelector('.submenu');
    submenu.classList.toggle('show');
  });
});