es6 Proxy

proxy在语言层面去操作一个对象

var user={};
        user.fname='Bob';
        user.lname="Wood";

        user.fullName= function () {
            console.log(this.fname+" "+this.lname);
        }
        user.fullName();//Bob Wood

现在要做到user.fullName就让它去显示。

proxy接收2个参数,第一个是对象{},第二个也是个{}。

var user = new Proxy({}, {
    get: function (obj, prop) {
        return obj.fname + " " + obj.lname;
    }
});
user.fname = 'Bob';
user.lname = "Wood";
console.log("user.fullName:" + user.fullName);      //user.fullName:Bob Wood

此时没有对传入get方法中的prop做判断。所以哪怕输入一个user.age也会输出:Bob Wood

console.log("user.age:" + user.age);      //user.age:Bob Wood

所以做一个判断,如果prop是full_name就输出全名

var user = new Proxy({}, {
    get: function (obj, prop) {
        if(prop=='full_name'){
            return obj.fname + " " + obj.lname;
        }
    }
});
user.fname = 'Bob';
user.lname = "Wood";
console.log("user.full_name:" + user.full_name);      //user.full_name:Bob Wood
console.log("user.age:" + user.age);      //user.age:undefined

也可以通过switch对多个prop进行处理

var user = new Proxy({}, {
    get: function (obj, prop) {
            switch (prop){
                case 'full_name':
                    return obj.fname + " " + obj.lname;
                case 'age':
                    return obj.age;
            }
    }
});
user.fname = 'Bob';
user.lname = "Wood";
user.age="25";
console.log("user.full_name:" + user.full_name);      //user.full_name:Bob Wood
console.log("user.age:" + user.age);      //user.age:25

总结:get就像一层过滤器一样,obj在取值前加了一层,在对象提取值之前做一些操作。

除了get,也可以用set在设置属性时做一层处理。

    var user = new Proxy({}, {
        get: function (obj, prop) {
            switch (prop) {
                case 'full_name':
                    return obj.fname + " " + obj.lname;
                case 'age':
                    return obj.age;
            }
        }, set: function (obj, prop,value) {//针对不同属性set值
            switch (prop) {
                case 'age':
                    obj.age=value+"岁";
                    break;
                default:
                    obj[prop]=value; //age之外的属性直接保存
                    break;
            }
        }
    });
    user.fname = 'Bob';
    user.lname = "Wood";
    user.age = "25";
    console.log("user.full_name:" + user.full_name);      //user.full_name:Bob Wood
    console.log("user.age:" + user.age);      //user.age:25岁

除了get ,set 还有一些方法如下:

var handler =
{
  // target.prop
  get: ...,
  // target.prop = value
  set: ...,
  // 'prop' in target
  has: ...,
  // delete target.prop
  deleteProperty: ...,
  // target(...args)
  apply: ...,
  // new target(...args)
  construct: ...,
  // Object.getOwnPropertyDescriptor(target, 'prop')
  getOwnPropertyDescriptor: ...,
  // Object.defineProperty(target, 'prop', descriptor)
  defineProperty: ...,
  // Object.getPrototypeOf(target), Reflect.getPrototypeOf(target),
  // target.__proto__, object.isPrototypeOf(target), object instanceof target
  getPrototypeOf: ...,
  // Object.setPrototypeOf(target), Reflect.setPrototypeOf(target)
  setPrototypeOf: ...,
  // for (let i in target) {}
  enumerate: ...,
  // Object.keys(target)
  ownKeys: ...,
  // Object.preventExtensions(target)
  preventExtensions: ...,
  // Object.isExtensible(target)
  isExtensible :...
}

 

 

 

参考:http://wiki.jikexueyuan.com/project/es6/object.html

MDN Proxy 

 

本文作者starof,因知识本身在变化,作者也在不断学习成长,文章内容也不定时更新,为避免误导读者,方便追根溯源,请诸位转载注明出处:http://www.cnblogs.com/starof/p/6919862.html有问题欢迎与我讨论,共同进步。

posted @ 2017-05-31 11:59  starof  阅读(301)  评论(0编辑  收藏