es6javascript的Proxy方法

var person = {
    name: " 张三 "
};
var proxy = new Proxy(person, {
    get: function(target, property) {
        if(property in target) {
            return target[property];
        } else {
            throw new ReferenceError("Property \"" + property + "\" does not exist.");
        }
    }
});
proxy.name // " 张三 "
proxy.age //  抛出一个错误set() 方法用来拦截某个属性的赋值操作。

let validator = {
    set: function(obj, prop, value) {
        if(prop === 'age') {
            if(!Number.isInteger(value)) {
                throw new TypeError('The age is not an integer');
            }
            if(value > 200) {
                throw new RangeError('The age seems invalid');
            }
        }
        //  对于 age 以外的属性，直接保存
        obj[prop] = value;
    }
};
let person = new Proxy({}, validator);
person.age = 100;
person.age // 100
person.age = 'young' //  报错
person.age = 300 //  报错