菜鸟教程在线编辑器

AI 编程工具
 
                <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Vue 测试实例 - 菜鸟教程(runoob.com)</title>
<script src="https://lf3-cdn-tos.bytecdntp.com/cdn/expire-1-M/vue/3.2.31/vue.global.min.js"></script>
</head>
<body>
<div id = "app">
    千米 : <input type = "text" v-model = "kilometers"  @focus="currentlyActiveField = 'kilometers'">
    米 : <input type = "text" v-model = "meters" @focus="currentlyActiveField = 'meters'">
</div>
<p id="info"></p>    
<script>
const app = {
  data() {
    return {
      kilometers : 0,
      meters:0
    }
  },
  watch : {
    kilometers:function(newValue, oldValue) {
      // 判断是否是当前输入框
      if (this.currentlyActiveField === 'kilometers') { 
        this.meters = newValue * 1000
      }
    },
    meters : function (newValue, oldValue) {
      // 判断是否是当前输入框
      if (this.currentlyActiveField === 'meters') {
        this.kilometers = newValue/ 1000;
      }
    }
  }
}
vm = Vue.createApp(app).mount('#app')
vm.$watch('kilometers', function (newValue, oldValue) {
  // 这个回调将在 vm.kilometers 改变后调用
  document.getElementById ("info").innerHTML = "修改前值为: " + oldValue + "，修改后值为: " + newValue;
})
</script>
</body>
</html>
              