Regular expression to validate username

Question

I\'m trying to create a regular expression to validate usernames against these criteria:

1. Only contains alphanumeric characters, underscore an

Answer 1

^[a-z0-9_-]{3,15}$

^ # Start of the line

[a-z0-9_-] # Match characters and symbols in the list, a-z, 0-9, underscore, hyphen

{3,15} # Length at least 3 characters and maximum length of 15

$ # End of the line