JavaScript Regular Expressions

All Major Credit Cards

This regular expression will validate all major credit cards: American Express (Amex), Discover, Mastercard, and Visa. Note that it is not quite as precise as its counterpart Perl and PHP regex.

    '^(?:4[0-9]{12}(?:[0-9]{3})?|5[1-5][0-9]{14}|6011[0-9]{12}|3(?:0[0-5]|[68][0-9])[0-9]{11}|3[47][0-9]{13})$'


Alpha-Numeric Characters

Test for alpha-numeric characters with this regexp.

    '^[a-zA-Z0-9]+$'

Alphabetic Characters

This regex will test for alphabetic characters only (upper and lowercase).

    '^[a-zA-Z]+$'

Canadian Postal Codes

Tests for valid Canadian Postal Codes.

        '^[ABCEGHJKLMNPRSTVXY][0-9][A-Z] [0-9][A-Z][0-9]$'

Date (MM/DD/YYYY)

Validate the calendar date in MM/DD/YYYY format with this regex. Optional separators are spaces, hyphens, forward slashes, and periods. The year is limited between 1900 and 2099.

    '^(0?[1-9]|1[012])[- /.](0?[1-9]|[12][0-9]|3[01])[- /.](19|20)?[0-9]{2}$'

Date (YYYY/MM/DD)

Validate the calendar date in YYYY/MM/DD format with this regex. Optional separators are spaces, hyphens, forward slashes, and periods. The year is limited between 1900 and 2099.

        '^(19|20)?[0-9]{2}[- /.](0?[1-9]|1[012])[- /.](0?[1-9]|[12][0-9]|3[01])$'Digits

This regex will test for digits (whole numbers).

    '^[0-9]+$'

Emails

This email regex is not fully RFC5322-compliant, but it will validate most common email address formats correctly.

      '^[a-zA-Z0-9._%-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}$'

Passwords

Test for a strong password with this regex. The password must contain one lowercase letter, one uppercase letter, one number, and be at least 6 characters long.

     "(?=^.{6,}$)((?=.*[A-Za-z0-9])(?=.*[A-Z])(?=.*[a-z]))^.*"

Phone Numbers (North American)

This regex will validate a 10-digit North American telephone number. Separators are not required, but can include spaces, hyphens, or periods. Parentheses around the area code are also optional.

    '^(([0-9]{1})*[- .(]*([0-9]{3})[- .)]*[0-9]{3}[- .]*[0-9]{4})+$'

URLs

This URL regex will validate most common URL formats correctly.

        '^((http|https|ftp)://)?([[a-zA-Z0-9]\-\.])+(\.)([[a-zA-Z0-9]]){2,4}([[a-zA-Z0-9]/+=%&_\.~?\-]*)$'

US ZIP Codes
This regexp verifies US ZIP Codes, with an optional 4 number ZIP code extension.

    '^[0-9]{5}(?:-[0-9]{4})?$'


Note : It will also work for Java only you need to remove ^ from begining and $ from last.

 Reference: Java Regular Expression Tutorial with Examples