1、undefined == false //返回false
2、null == false //返回false
3、undefined == null //返回true
4、undefined === null //返回false
1、undefined == false //返回false
2、null == false //返回false
3、undefined == null //返回true
4、undefined === null //返回false
原文：http://www.cnblogs.com/wuqiuxue/p/8038731.html