Use watch to monitor attributes in WeChat applets

app.js set listener setWatcher

App({
  /**
   * 监听属性 并执行监听函数
   */
  observe(obj, key, watchFun, that) {
    var val = obj[key]; // 给该属性设默认值
    Object.defineProperty(obj, key, {
      configurable: true,
      enumerable: true,
      set: function (value) {
        val = value;
        watchFun(value, val, that); // 赋值(set)时，调用对应函数
      },
      get: function () {
        return val;
      }
    })
  }, 
 /**
   * 设置监听器
   */
  setWatcher(data, watch, that) {
    Object.keys(watch).forEach(v => {
      let key = v.split('.'); // 将watch中的属性以'.'切分成数组
      let nowData = data; // 将data赋值给nowData
      for (let i = 0; i < key.length - 1; i++) { // 遍历key数组的元素，除了最后一个！
        nowData = nowData[key[i]]; // 将nowData指向它的key属性对象
      }
      let lastKey = key[key.length - 1];
      // 假设key==='my.name',此时nowData===data['my']===data.my,lastKey==='name'
      this.observe(nowData, lastKey, watch[v], that); // 监听nowData对象的lastKey
    })
  },
})

use

let app = getApp();

Page({
  /**
   * 生命周期函数--监听页面加载
   */
  onLoad: function (options) {
    app.setWatcher(this.data, this.watch, this); // 设置监听器
  }
  watch: {
   'oilCardInfo.accountType': (newV, oldV, that) => {
      that.maxOilBindCount()
    }
  },
})