<div id="watch"> <input type="text" v-model="msg"> {{msg}} <button @click="update"></button> </div> < <script> var all={el:'#watch', data:{msg:'fddgssdg'}, methods:{ update:function () { this.msg='我草your mother'; } }}; var v=new Vue(all); var callback=function (val,oldVal) { alert('new val==='+val); alert('old val==='+oldVal); } v.$watch('msg',callback); </script>