In the resent past I had to write some simple regular expressions.
So thought of sharing them with you.
An EMail Address Validator
^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)(([a-zA-Z0-9\-]+\.)+))([a-zA-Z]{2,4}[0-9]{1,3})(\]?)$
This will validate the entered EMail address.
A Password Validator
(?=.{6,})[a-zA-Z]+[^a-zA-Z]+[^a-zA-Z]+[a-zA-Z]+
This will validate the password to have at least 1 alphabetic character and 1 numeric digit, and altogether the password will be more than 6 characters long.
A Telephone Number Valdator
\d{4}\s\d{3}\s\d{6}
This will expect the telephone number to be in international format. For example (0094 777 123456).
A Simple Length Validator
[\s\S]{1,200}
This will allow only only 200 or lesser characters for input.
A Length Validator Which Works With Linefeed (Return, Enter)
^(.\n){0,500}$
This will validate and allow only 500 input even in a multi line field when linefeed (enter) is used in between.
A Date Validator
(0[1-9]1[012])[- /.](0[1-9][12][0-9]3[01])[- /.](1920)\d\d
This will check for the date validness. The date format should be mm/dd/yyyy to correctly validate by this.
If the date format is required as yyyy/mm/dd then use the following.
(1920)\d\d[- /.](0[1-9]1[012])[- /.](0[1-9][12][0-9]3[01])
Following are some good sites that you can refer for regular expression help.