Proxy深度代理

let obj = {
  name: 'crap',
  age:{
    n: 1
  }
}
let arr = [1, 2, 3]

function update() {
  console.log('update');
}
let handler = {
  get(target, key) {
    if(typeof target[key] === 'object'){
      return new Proxy(target[key], handler);
    }
    return Reflect.get(target, key);
  },
  set(target, key, val) {
    if (key === 'length') return true;
    update();
    return Reflect.set(target, key, val);
  }
}
// let proxy = new Proxy(arr, handler)

// proxy.push(111); //definProperty不能监控后来增加的属性 vm.$set()
// console.log(arr);

let proxy = new Proxy(obj, handler);
proxy.age.n = 100;
console.log(obj);