简单介绍 javascript 中 __proto__ 属性的原理
http://blog.csdn.net/shi0090/article/details/45008595
http://blog.csdn.net/chunqiuwei/article/details/22092551
http://blog.csdn.net/shi0090/article/details/45008595
http://blog.csdn.net/chunqiuwei/article/details/22092551