getter and setter

(function () {
    var o = {
        a : 7,
        get b(){return this.a +1;},//通过 get,set的 b,c方法间接性修改 a 属性
        set c(x){this.a = x/2}
    };
    console.log(o.a);
    console.log(o.b);
    o.c = 50;
    console.log(o.a);
})();

(function () {
    var o = null;
    o = Object.create(Object.prototype,//指定原型为 Object.prototype
            {
                bar:{
                    get :function(){
                        return 10;
                    },
                    set : function (val) {
                        console.log("Setting `o.bar` to ",val);
                    }
                }
            }//第二个参数
        );
    console.log(o.bar);
    o.bar = 12;
})();