vue源码学习之Object.defineProperty对象属性监听

let a = {'b': 1};Object.defineProperty(a, 'b', {  enumerable: false,  configurable: false,  get: function(){    console.log('b' + '被访问');  },  set: function(newVal){    console.log('b' + '被修改，新' + 'b' + '=' + newVal);  }});a.b = 2;  // b被修改，新b=2a.b;    // b被访问

// 观察者构造函数function Observer(data){  this.data = data;  this.walk(data);}let p = Observer.prototype;p.walk = function(obj){  let val;  for(let key in obj){    // 通过 hasOwnProperty 过滤掉一个对象本身拥有的属性     if(obj.hasOwnProperty(key)){      val = obj[key];      // 递归调用 循环所有对象出来      if(typeof val === 'object'){        new Observer(val);      }      this.convert(key, val);    }  }};p.convert = function(key, val){  Object.defineProperty(this.data, key, {    enumerable: false,    configurable: false,    get: function(){      console.log(key + '被访问');    },    set: function(newVal){      console.log(key + '被修改，新' + key + '=' + newVal);      if(newVal === val) return ;      val = newVal;    }  })};let data = {  user: {    name: 'zhangsan',    age: 14  },  address: {    city: 'beijing'  }}let app = new Observer(data);data.user.name;  // user被访问