SOURCE

new Vue({
  el: '#app',  
	components: {
  'child': {
  	props: ['myMessage', 'counter'],
		template: '<div><p class="message">{{myMessage}} : {{counter}}</p> <input type="button" @click="cadd" value="子组件测试"></div>',
    methods: {
    	cadd() {
      	this.counter += 1
        this.$emit('update:counter', this.counter)
      }
    }
 	 }
  },
  data: {
    parentMsg: 'Hello Vue.js!',
    count: 1
  },
  methods: {
  	add() {
    	return this.count+=1
    }
  }
})

<script src="https://unpkg.com/vue"></script>

<div id="app">
  <input v-model="parentMsg">
  <p>计数器：{{count}}</p>
  <input type="button" @click="add" value="加 1">
  <br>
  <child v-bind:my-message="parentMsg" :counter.sync="count"></child>
</div>