const obj = {
  _name: 'zjf',
  age: 21
}

// 监听所有属性
Object.keys(obj).forEach(key => { // 缺点多
  let value = obj[key];
  Object.defineProperty(obj, key, {
    get: function() {
      console.log(`监听到obj的${key}属性被访问`);
      return value;
    },
    set: function(newValue) {
      console.log(`监听到obj的${key}属性被设置值`);
      value = newValue;
    }
  })
})

obj._name = 'why';
obj.age = 22;
console.log(obj._name);
console.log(obj.age);