首先组件要足够语义化，就是开发者尽量少看文档描述也可以看出怎么用，

以下是结构

然后编写dropdown-item组件，此处的disabled控制item是否可选，里面的选项通过插槽的形式获取

<template>
  <li
    class="dropdown-option"
    :class="{'is-disabled': disabled}"
  >
    <slot></slot>
  </li>
</template>

<script lang="ts">
import { defineComponent } from 'vue'
export default defineComponent({
  props: {
    disabled: {
      type: Boolean,
      default: false
    }
  }
})
</script>

<style>
.dropdown-option.is-disabled * {
  color: #6c757d;
  pointer-events: none;
  background-color: transparent;
}
</style>

 编写dropdown组件

<template>
<div class="dropdown" ref="dropdownRef">
  <a href="#" class="btn btn-outline-light my-2 dropdown-toggle" @click.prevent="toggleOpen">
    {{title}}
  </a>
  <ul class="dropdown-menu" :style="{display: 'block'}" v-if="isOpen">
    <slot></slot>
  </ul>
</div>
</template>

<script lang="ts">
import { defineComponent, ref, watch } from 'vue'
import useClickOutside from '../hooks/useClickOutside'
export default defineComponent({
  name: 'Dropdown',
  props: {
    title: {
      type: String,
      required: true
    }
  },
  setup() {
    const isOpen = ref(false)
    const dropdownRef = ref<null | HTMLElement>(null)
    const toggleOpen = () => {
      isOpen.value = !isOpen.value
    }
    const isClickOutside = useClickOutside(dropdownRef)

    watch(isClickOutside, () => {
      if (isOpen.value && isClickOutside.value) {
        isOpen.value = false
      }
    })
    return {
      isOpen,
      toggleOpen,
      dropdownRef
    }
  }
})
</script>

 使用到控制展开收起下拉菜单的函数useClickOutside

该函数可以判断点击是否在元素内部

import { ref, onMounted, onUnmounted, Ref } from 'vue'

const useClickOutside = (elementRef: Ref<null | HTMLElement>) => {
  const isClickOutside = ref(false)
  const handler = (e: MouseEvent) => {
    if (elementRef.value) {
      if (elementRef.value.contains(e.target as HTMLElement)) {
        isClickOutside.value = false
      } else {
        isClickOutside.value = true
      }
    }
  }
  onMounted(() => {
    document.addEventListener('click', handler)
  })
  onUnmounted(() => {
    document.removeEventListener('click', handler)
  })
  return isClickOutside
}

export default useClickOutside

 在组件中使用

<dropdown :title="`你好 ${user.nickName}`">
          <dropdown-item><a href="#" class="dropdown-item">新建文章</a></dropdown-item>
          <dropdown-item><a href="#" class="dropdown-item">我的专栏</a></dropdown-item>
          <dropdown-item disabled><a href="#" class="dropdown-item">编辑资料</a></dropdown-item>
          <dropdown-item><a href="#" class="dropdown-item">退出登陆</a></dropdown-item>
        </dropdown>