Firefox gives SyntaxError: invalid regexp group

Question

I have few regular expression used for form validation and I noticed that my project is not accessible through firefox as it shows nothing! but give the error in the console, SyntaxError: invalid regexp group

nicRegex is checking for National Identity Card in my country. Format should be 937962723V or 937962723X or any 11 digit number according to the current format.

phoneRegex is to check phone numbers with my country code. 94121212121 or 0762323232

const nicRegex = /^(?:19|20)?\d{2}(?:[01235678]\d\d(?<!(?:000|500|36[7-9]|3[7-9]\d|86[7-9]|8[7-9]\d)))\d{4}(?:[vVxX])$/;

You could try each of them in the console to find out which is wrong — derpirscher, Apr 20 '19 at 13:40
You should at least know *which* REGEX is problematic. That will be denoted by the line number attached to the error. — Mitya, Apr 20 '19 at 13:41
It doesn't give any particular line number but bundle.js:1:34. of bundle.js — Hasini Silva, Apr 20 '19 at 13:43
@Utkanos I found the culprit. It's `const nicRegex = /^(?:19|20)?\d{2}(?:[01235678]\d\d(?<!(?:000|500|36[7-9]|3[7-9]\d|86[7-9]|8[7-9]\d)))\d{4}(?:[vVxX])$/;` — Hasini Silva, Apr 20 '19 at 13:47
`nicRegex` contains a *negative lookbehind* - this is not supported in FF. — Alex K., Apr 20 '19 at 13:48
Well you would need to rewrite it so that it didn't need to use one, the way you actually do that depends on the rules of the format your trying to validate. Also see https://stackoverflow.com/questions/641407/javascript-negative-lookbehind-equivalent — Alex K., Apr 20 '19 at 14:00
That was helpful @AlexK. I rewrote a simple regrex and it's working. — Hasini Silva, Apr 20 '19 at 14:25

score 9 · Answer 1 · edited Jun 20 '20 at 09:12

9

TLDR; Use named capture groups with caution (or just don't use them)

For me, it was because I thought I'd be clever and try to used named capture groups in my regex... Firefox punished me.

Doesn't work: /(?<text>[a-z]+)/

Does work: /([a-z]+)/

edited Jun 20 '20 at 09:12

Community

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answered Oct 03 '19 at 14:26

Nick Grealy

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Wiktor Stribiżew · Accepted Answer · 2021-09-21T09:15:33.423

The negative lookbehind (not currently supported in Safari) is used here to restrict the previous three digits. This restriction can be performed equally well with a negative lookahead, just it needs to be placed before the 3-digit pattern:

(?:[0-35-8]\d\d(?<!(?:000|500|36[7-9]|3[7-9]\d|86[7-9]|8[7-9]\d)))

should look like

(?!000|500|36[7-9]|3[7-9]\d|86[7-9]|8[7-9]\d)[0-35-8]\d\d

Note the non-capturing groups are redundant here, I removed them, and [01235678] = [0-35-8].

The final regex looks like

/^(?:19|20)?\d{2}(?!000|500|36[7-9]|3[7-9]\d|86[7-9]|8[7-9]\d)[0-35-8]\d\d\d{4}[vVxX]$/

See the regex demo and the Regulex graph:

Firefox gives SyntaxError: invalid regexp group

2 Answers2

TLDR; Use named capture groups with caution (or just don't use them)

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