Vue.component('ParentA',{
  template:`
    <div id="parent-a">
      <h2>Parent A</h2>
      <pre>data {{ this.$data }}</pre>
      <button @click="reRender">Rerender Parent</button>
      <hr/>
      <child-a :score="score"/>
      <child-b/>
    </div>`,
  data() {
    return {
      score: 100
    }
  },
  methods: {
    reRender() {
      this.$forceUpdate();
    }
  }
})