// 数据绑定的构造函数
function Observer(data) {
 this.data = data;

 for(var key in data) {
  if(data.hasOwnProperty(key)) {
   var val = data[key];
   if(typeof data[key] === "object"){
    // 如果值不为原始类型，则继续递归
    new Observer(val);
   }else {
    this.convert(key, val);
   }
  }
 }
}
// 定义set 和 get函数
Observer.prototype.convert = function(key, val) {
 Object.defineProperty(this.data, key, {
  enumerable: true,
  confingurable: true,
  get: function() {
   console.log(key + "被访问了");
   return val;
  },
  set: function(newVal) {
   console.log(key + "被设置了新值" + newVal);
   val = newVal;
  }
 });
}
var app = new Observer({name: "xieshuai", age: 24, address: {city: "shenzheng"}});

app.data.name;  // name被访问了
app.data.age = 18; // age被设置了新值18