export default {
 props:{
 name:{
 type:String
 }
 },
 data () {
 return {
 author: "Jinkey"
 }
 },
 mounted:function(){
 this.author = 'lili'
 },
 watch:{
 name:function(){
 console.log(this.name);
 },
 author:function(){
 console.log('lili');
 }
 }
}

<firstcomponent :name="name"></firstcomponent>

import firstcomponent from './component/firstcomponent.vue'
export default {
 data () {
 return {
 msg: 'Hello Vue!',
 name:'lili'
 }
 },
 components: { firstcomponent}
}