In Vue, how do I get the emitted value from a child component and then use it in the parent component's return data?

Question

How to get the title value passed by the Topbar component and use the value in the data() return part? I tried adding a method to pass the value, but unfortunately, although I was able to console log the value in the parent file, it didn't work. I'm still a beginner in vue js so I'd like some help on this issue. Thanks!

<template>
    <div>
        <Topbar :tabs='tabs' @pass-data="getTabTitle"/>
        
    </div>
</template>
<script>
    import Topbar from "../components/Navigation/Topbar.vue";

    export default {
        name: "Progress",
        components: {
            Topbar,
    },  
        
        data() {
            return {
                title:'',//have the emitted value here
                tabs: [  
                    {
                        link:'',
                        name: "Sec 1",
                        dropdown: false,
                        dropdownTabs:[]
                    },
                    {
                        link:'',
                        name: "Sec 2",
                        dropdown: false,
                        dropdownTabs:[]
                    }
                ]
            }
    },
          methods: {
            getTabTitle(title) {
                console.log(title)
                this.title =title
        }
    },
    }
</script>

Top bar template

<template>
  <ul class="navbar-nav">
                    
       <li @click="onClick(tab.name)"
                        v-for="(tab, index) in tabs.filter((tab)=> tab.dropdown===false)" :key="index">
                        {{tab.name}}
                    </li>
      <DropdownMenu v-for="(tab, index) in tabs.filter((tab)=> tab.dropdown===true)" :key="index"
                        :tab="tab" />

  </ul>
</template>

<script>
    import DropdownMenu from "./DropdownMenu.vue";

    export default {
        name: "Topbar",
        props: {
            tabs: Array
        },
        components: {
            DropdownMenu,

    },
     methods: {
        onClick(tabName) {
            this.$emit('pass-data',tabName)
        }
    }   

    }
</script>

Answer 1

Try a code snippet like below (pass all tabs to child and loop there):

const app = Vue.createApp({
  data() {
    return {
      title:'',
      tabs: [  
        {link:'', name: "Sec 1", dropdown: false, dropdownTabs:[]},
        {link:'', name: "Sec 2", dropdown: false, dropdownTabs:[]}
      ]
    }
  },
  methods: {
    getTabTitle(title) {
      console.log(title)
      this.title =title
    }
  }
})
app.component('topbar', {
  template: `
    <div v-for="(tab, i) in tabs" :key="i">
      <button @click="send(tab.name)">{{ tab.name }}</button>
    </div>
  `,
  props: ['tabs'],
  methods: {
    send(title) {
      this.$emit('passData', title)
    }
  }
})
app.mount('#demo')

<script src="https://unpkg.com/vue@3/dist/vue.global.prod.js"></script>
<div id="demo">
  <b>{{ title }}</b>
  <topbar :tabs='tabs' @pass-data="getTabTitle"></topbar>
</div>