Dropdown3.vue

// Dropdown.vue (parent)

<template>
  <div>
    <button @click="showMenu = !showMenu">Click me</button>
    <dropdown-menu v-if="showMenu" :items="items" @select-option="onOptionSelected"></dropdown-menu>
  </div>
<template>
<script>
 export default {
  props: {
   items: Array
  },
  data() {
   return {
     selectedOption: null,
     showMenu: false
   }
  },
  methods: {
    onOptionSelected(option) {
      this.selectedOption = option
      this.showMenu = true
    }
  }
 }
</script>

// DropdownMenu.vue (child)

<template>
  <ul>
    <li v-for="item in items" @click="selectOption(item)">{{item.name}}</li>
  </ul>
<template>
<script>
 export default {
  props: {
   items: Array
  },
  methods: {
    selectOption(item) {
     this.$emit('select-option', item)
    }
  }
 }
</script>