Proxy监听对象的数据变化，处理绑定数据很有用

var peo = { name: 'zhangsan', salary: 27 };
//interceptor 拦截
var interceptor = {
set: function (recObj, key, value) {
console.log(key, 'is changed to', value); //name is changed to lisi
recObj[key] = value;
}
};
//创建代理以进行侦听
proxyEngineer = new Proxy(peo, interceptor);
//做一些改动来触发代理
proxyEngineer.name = 'lisi';//控制台输出：salary is changed to 60
console.log(peo) //{name: "lisi", salary: 27}