regular expression alphanumeric characters - allowing hyphens and underscores

Question

I need a Regular Expression for Javascript that checks if a password is correct only when

• Has at least 1 number and 1 letter
• Is still valid when it has an underscore and/or a hyphen
• Must be 4-20 characters long.

Examples:

1. test123 -> Valid
2. test1 -> valid
3. 1234 ->invalid
4. test -> invalid
5. test1_ -> valid
6. test-2 -> valid

I tried using

var Reg = /^(?=.*\d)(?=.*[A-Za-z])[0-9A-Za-z-_]{4,12}$/;

It works in PHP, but not in Javascript, any suggestions?

Answer 1

Put the hyphen at the end of the character class:

var Reg = /^(?=.*\d)(?=.*[A-Za-z])[0-9A-Za-z_-]{4,20}$/;

You can also shorten that character class:

var Reg = /^(?=.*\d)(?=.*[A-Za-z])[\w-]{4,20}$/;

Also, you said 20 characters, not 12. Right?