ar reg = /(((^https?:(?://)?)(?:[-;:&=+$,w]+@)?[A-Za-z0-9.-]+|(?:www.|[-;:&=+$,w]+@)[A-Za-z0-9.-]+)((?:/[+~%/.w-_]*)???(?:[-+=&;%@.w_]*)#?(?:[w]*))?)$/;
http://www.baidu.com -------正确
www.baidu.com -------正确
baidu.com -------错误
http://123.com -------正确