SOURCE

Vue.component('form-component', {
  template: '#form',
  props: ['value'],
  methods: {
    onInput(event){
      this.emit('input', event.target.value);
    }
  }
})

Vue.component('hello-component', {
  template: '#hello',
  props: ['user'],
  data: function() {
    return {
      msg: 'hello'
    }
  }
})

new Vue({
  el: '#app',
  data() {
    return {
      user: 'zs'
    }
  }
})

<template id="form">
  <div>
    <label for="name">
      type your name:
    </label>
    <input type="text" :value="value" id="name" @input="onInput"/>
  </div>
</template>
<template id="hello">
  <h1>
    {{msg}} {{user}}
  </h1>
</template>
<div id="app">
  <form-component :user="user">
  </form-component>
  <hello-component :user="user">
  </hello-component>
</div>