Need a regular expression - disallow all zeros

Question

I want to validate a string to meet the following conditions:

• Must be 6 characters long
• Only the first character can be alpha-numeric the rest must be

Answer 1

You can use a (?!0+$) negative lookahead to avoid matching a string that only contains 1 or more zeros:

/^(?!0+$)[A-Z0-9][0-9]{5}$/
  ^^^^^^^

See the regex demo. This approach lets you just copy/paste the lookahead after ^ and not worry about how many chars the consuming part matches.

Details

• ^ - start of a string
• (?!0+$) - a negative lookahead that fails the match if there are 1 or more 0 chars up to the end of the string ($)
• [A-Z0-9] - an uppercase ASCII letter or a digit
• [0-9]{5} - five digits
• $ - end of string.