Vue2 adding data is not a responsive processing method

data:{
    person:{
       name:"张三",
       hobby:["打篮球","游泳","健身"]
    }
}



addData() {
    this.person.age=18;
    this.$set(this.person,"age",19)
    this.person=Object.assign({},this.person,{age:20})
    this.$set(this.person.hobby,0,"吃吃")
}