<div id="demo">
    <h1>汇率转换</h1>
    <div class="moneyBox"><span>cny</span><input v-model="cny" type="text"><span>人民币￥</span></div>
    <div class="moneyBox"><span>usd</span><input v-model="usd" type="text"><span>美元$</span></div>
    <div class="moneyBox"><span>hkd</span><input v-model="hkd" type="text"><span>港币$</span></div>
  </div>

var CNY_USD = 6.96;
  var CNY_HKD = 0.90;
  var data={  cny:'100',
        usd:'14.38'  ,
        hkd:'111.53',
      };
  var myVue = new Vue({
   el: '#demo',
   data: data,
   computed: {
     usd:{
       get: function() {
         return (this.cny/CNY_USD).toFixed(2);
       },
       set: function(newValue) {
         this.cny = (newValue*CNY_USD).toFixed(2);
       }
     },
     hkd:{
       get: function() {
         return (this.cny/CNY_HKD).toFixed(2);
       },
       set: function(newValue) {
         this.cny = (newValue*CNY_HKD2Q).toFixed(2);
       }
     }
   }
   })

.moneyBox{
      font-size: 20px;
      font-family: "微软雅黑";
    }
    .moneyBox input{
      width: 100px;
      height: 24px;
      padding: 0 10px;
      margin: 0 10px;
      border-radius: 5px;
      border: 1px solid #333;
    }