我想实现带有子菜单项的动态菜单。为此，我定义了一个数据对象，它包含所有带有子菜单项的菜单项。

<script setup lang="ts">
import { ref } from "vue";

const menu = ref([
  {
    id: 1,
    name: "Programs",
    submenu: ["Sub-1", "Sub-2", "Sub-3", "Sub-4"],
  },
  { id: 2, name: "Events", submenu: [] },
  { id: 3, name: "Publications", submenu: [] },
  { id: 4, name: "Tutorials", submenu: ["Tut-1", "Tut-2"] },
  { id: 5, name: "About Us", submenu: [] },
]);
</script>

在模板内，我在各自的html标签内调用这些菜单和子菜单：

<template>
  <div class="container mx-auto max-w-screen-xl">
    <!--Navbar-->
    <div
      class="menu-line align-baseline justify-around hidden w-full mb-2 md:block"
    >
      <ul
        class="font-BPGBannerCaps text-sm flex flex-col justify-end tracking-wide bg-gray-50 border border-gray-100 md:flex-row md:space-x-8 md:mt-0 md:mb-0 md:text-base md:font-medium md:border-0 md:bg-white"
      >
        <li v-for="item in menu" :key="item.id">
          <button
            id="dropdownNavbarLink"
            data-dropdown-toggle="dropdownNavbar"
            class="flex justify-between items-center w-full font-medium text-gray-700 rounded hover:bg-gray-100 md:hover:bg-transparent md:border-0 md:hover:text-blue-700 md:p-0 md:w-auto"
          >
            {{ item.name }}
            <svg
              v-if="item.submenu.length"
              class="ml-1 w-5 h-5"
              aria-hidden="true"
              fill="currentColor"
              viewBox="0 0 20 20"
              xmlns="http://www.w3.org/2000/svg"
            >
              <path
                fill-rule="evenodd"
                d="M5.293 7.293a1 1 0 011.414 0L10 10.586l3.293-3.293a1 1 0 111.414 1.414l-4 4a1 1 0 01-1.414 0l-4-4a1 1 0 010-1.414z"
                clip-rule="evenodd"
              ></path>
            </svg>
          </button>
          <!-- Dropdown menu -->
          <div
            id="dropdownNavbar"
            class="hidden z-10 w-56 font-normal bg-white rounded divide-y divide-gray-100 shadow"
          >
            <ul
              class="py-1 text-sm text-gray-700 dark:text-gray-400"
              aria-labelledby="dropdownLargeButton"
              v-if="item.submenu.length"
            >
              <li v-for="subitem in item.submenu" :key="item.id">
                <a href="#" class="block py-2 px-4 hover:bg-gray-100">{{
                  subitem
                }}</a>
              </li>
            </ul>
          </div>
        </li>
      </ul>
    </div>
  </div>
</template>

但是，会为任何菜单项显示子菜单项：

善意的建议我做错了什么，我怎么能解决这个问题。