Vue 侦听器

侦听器

1. 侦听器的应用场景

数据变化时执行异步或开销较大的操作

2. 侦听器的用法

watch: {
    firstName: function(val){ // val表示变化之后的值 
       this.fullName = val + this.lastName;
     },
    lastName: function(val) {
       this.fullName = this.firstName + val;
    }
}

基本用法

  <div id="app">
    <div>
      <span>名：</span>
      <span>
        <input type="text" v-model='firstName'>
      </span>
    </div>
    <div>
      <span>姓：</span>
      <span>
        <input type="text" v-model='lastName'>
      </span>
    </div>
    <div>{{fullName}}</div>
  </div>

  <script type="text/javascript">
    /*
      侦听器
    */
    var vm = new Vue({
      el: '#app',
      data: {
        firstName: 'Jim',
        lastName: 'Green',
        fullName: 'Jim Green'
      },
      watch: {
        firstName: function(val) {
          this.fullName = val + ' ' + this.lastName;
        },
        lastName: function(val) {
          this.fullName = this.firstName + ' ' + val;
        }
      }
    });
  </script>