Regex - Match only if input does not contain all letters

Question

I understand the regex used to match if it contains all letters is ^[a-zA-Z]+$ so I thought a negation of this regex would be the answer and tried ^(?!^[a-zA-Z])+$ but it doesn't seem to work.

To provide some context, I'm creating a basic form using SurveyJS form creator that accepts custom validation only via regex. A certain form input should allow users to input anything and only throw an error if the user only fill in letters.

I don't know Regex that much, but I just want to point out that you have visual tools to debug your regex! https://regex101.com/ — levisnkyyyy, Sep 09 '20 at 06:36
Provide examples, please. Which inputs must be validated as good and which as bad. — MadRay, Sep 09 '20 at 06:40
`^(?!.*[A-Za-z]).*$` Here is the [visualization](https://www.debuggex.com/r/5bqXLRis3VsTWj8j) — Gurmanjot Singh, Sep 09 '20 at 06:41

Patrick Artner · Accepted Answer · 2020-09-09T06:45:01.390

1

You can use

^(?![a-zA-Z]+$).*

The negative lookahead ensures the whole line does not only contain a-zA-Z till the $ (end of line - thats why its included inside the lookahead - not outside of it) and the .* afterwards would match anything that passes the negative lookahead.

Demo: https://regex101.com/r/QuC2SQ/1

edited Sep 09 '20 at 06:45

answered Sep 09 '20 at 06:39

Patrick Artner

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Regex - Match only if input does not contain all letters

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