Proxy Reflect

Proxy 可以理解成，在目标对象之前架设一层“拦截”，外界对该对象的访问，都必须先通过这层拦截，因此提供了一种机制，可以对外界的访问进行过滤和改写。Proxy 这个词的原意是代理，用在这里表示由它来“代理”某些操作，可以译为“代理器”。

{
    //类似于供应商的数据对象
    let obj = {
        time:'2019-12-13',
        name:'net',
        _r:123
    }
    //代理商
    let monitor = new Proxy(obj,{
        //代理操作
        //拦截对象属性的读取
        get(target,key){  //target指代理对象，key是键值
            return target[key].replace('2019','2020')
        },
        // 拦截对象设置
        set(target,key,value){
            if(key === 'name'){
                return target[key] = value;
            }else{
                return target[key];
            }
        },
        // 拦截 key in  object 操作
        has(target,key){
            if(key === 'name'){
                return target[key]
            }else{
                return false;
            }
        },
        // 拦截删除
        deleteProperty(target,key){
            if(key.indexOf('_') > -1){
                delete target[key];
                return true;
            }else{
                return target[key]
            }
        },
        // 拦截Object.keys,Object.getOwnPropertySymbols,Object.getOwnPropertyNames
        ownKeys(target){
            return Object.keys(target).filter(item=>item!='time')  //Object.keys(target)取出原始对象的key值
        }
    });
    //用户直接操作minotor
    console.log('get',monitor.time)

    monitor.time='2019';
    monitor.name='sss';
    console.log('set',monitor.time,monitor)

    console.log('has','name' in monitor,'time' in monitor)  //true false
    
    // delete monitor.time;
    // console.log('delete',monitor)

    // delete monitor._r;
    // console.log('delete',monitor)

    console.log('ownkeys',Object.keys(monitor))  //过滤属性

}

Reflect

{
    let obj = {
        time:'2019-12-13',
        name:'net',
        _r:123
    };
    console.log('reflect get',Reflect.get(obj,'time')); //Reflect 不需要new, get语法，对象，key值
    Reflect.set(obj,'name','bsq');
    console.log('set',obj)

    console.log('has',Reflect.has(obj,'name'))
}

实例运用

{
    // 应用
    function validator(target,validator){
        return new Proxy(target,{
            _validator:validator,
            set(target,key,value,proxy){
                if(target.hasOwnProperty(key)){
                    let va = this._validator[key];
                    if(!!va(value)){
                        return Reflect.set(target,key,value,proxy);
                    }else{
                        throw Error(`不能设置${key}为${value}`)
                    }    
                }else{
                    throw Error(`${key} 不存在`)
                }
            }
        })
    }
    const personValidators={
        name(val){
            return typeof val === 'string'
        },
        age(val){
            return typeof val ==='number'  && val>18
        }
    }
    class Person{
        constructor(name,age){
            this.name=name;
            this.age=age;
            return validator(this,personValidators)
        }
    }
    const person = new Person('lilei',30);
    console.log(person)
    // person.age='dd';
    // console.log(person)   //index.js:9736 Uncaught Error: 不能设置age为dd
    person.name='han meimei'
    console.log(person)
}