Question

I need a regular expression that makes sure that a string contains at least 3 different characters (of any type).

Example, aqaqaq is not valid because it is comprised of 2 different characters only.
aqwaqa or aq3aqa or aq!aqa are valid.

Is that possible in regex?

Languages: Javascript / PHP

Thanks

Answer 1

You can use this regular expression containing negative lookaheads:

/(.).*(?!\1)(.).*(?!\1)(?!\2)(.)/

Examples:

> regex = /(.).*(?!\1)(.).*(?!\1)(?!\2)(.)/
> regex.exec('abab!aba')
["abab!ab", "a", "!", "b"]
> regex.exec('abababa')
null