‘‘ == ‘0‘ //false 0 == ‘‘//true; 0 == ‘0‘//true ‘ \t\r\n ‘==0//true
null == undefined //true
false == ‘false‘//false false == ‘0‘//false false == null//false null == undefined //true
var a = 0, b = {}; a == b//false
请始终使用===和!===
原文：http://www.cnblogs.com/liyunhua/p/4621925.html