<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>Document</title> <script src="js/vue.js"></script> </head> <body> <div id="app"> <input type="text" v-model="firstname">+ <input type="text" v-model="lastname">= <input type="text" v-model="fullname"> </div> <script> //创建Vue实例,得到 ViewModel var vm = new Vue({ el: '#app', data: { firstname: '', lastname: '', fullname: '' }, methods: {}, watch: { //使用这个属性，可以监视data中指定数据的变化，然后触发这个watch中对应的function处理函数 firstname: function (newVal, oldVal) { //function可加可不加引号，但当时连字符命名时，必须要加 // this.fullname=this.firstname + '-' + this.lastname; this.fullname = newVal + '-' + this.oldVal; }, lastname:function(newVal){ this.fullname=this.firstname +"-" + newVal; } } }); </script> </body> </html>