小程序实现全局监听globalData数据变化

小程序项目开发想实现全局监听globalData数据变化，可参考数据劫持的实现方式，代码如下：
app.js

globalData: {
  msgTotal: ''
},
// 使用数据劫持模式监听数据变化
 observe(obj, key, watch, that) {
      let val = obj[key]; 
      Object.defineProperty(obj, key, {
        configurable: true,
        enumerable: true,
        set: function (value) {
          watch(val, value, that); 
          val = value;
        },
        get: function () {
          return val;
        }
      })
  }

页面赋值msgTotal

const app = getApp()
Page({
  setMsgTotal() {
    app.globalData.msgTotal = res.data.total
  }
})

组件内监听msgTotal

const app = getApp()
methods: {
    watch (oldVal, newVal, that) {
          that.setData({
            msgTotal: newVal
          })
     }
},
// 组件生命周期
lifetimes: {
   // 组件进入页面节点树执行
    attached() {
        app.observe(app.globalData, "msgTotal", this.watch, this);
    }
}

小程序页面监听msgTotal

const app = getApp()
Page({
   onReady() {
        app.observe(app.globalData, "msgTotal", this.watch, this);
   },
   watch (oldVal, newVal, that) {
       that.setData({
         msgTotal: newVal
       })
   }
})