vue 之监听事件----2.watch 

<!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>

 

posted @ 2020-03-19 09:29  一只小菜鸟呀！  阅读(586)  评论(0)    收藏  举报