Regex - unhandled js exception in react native

Question

I am using the following regex in my react-native app.

This is an email validation regex :

^[\w]+@((?:[A-Za-z0-9](?:[A-Za-z0-9-]{0,61}[A-Za-z0-9])?\.)+)(?:[A-Za-z0-9-]{2,63}(?<!-))

This works fine in the browser but crashes the react native app due to the following :

no stack', reason: 'Unhandled JS Exception: Invalid regular expression: invalid group specifier name

Could someone please help getting this to work on react native, maybe by achieving the same thing that this regex achieves but without the lookbehind expression ?

Does this answer your question? [no stack', reason: 'Unhandled JS Exception: Invalid regular expression: invalid group specifier name](https://stackoverflow.com/questions/56990784/no-stack-reason-unhandled-js-exception-invalid-regular-expression-invalid) — Muhammad Usama Ashraf, Sep 13 '21 at 09:39

Tim Biegeleisen · Accepted Answer · 2021-09-13T10:04:43.773

1

The problem is likely caused the by the (?<!-) negative lookahead at the end of the regex pattern, which your JavaScript engine does not support. To ensure that a hyphen does not occur at the end of the email, we can simply use:

^[\w]+@((?:[A-Za-z0-9](?:[A-Za-z0-9-]{0,61}[A-Za-z0-9])?\.)+)(?:[A-Za-z0-9-]{1,62}[A-Za-z0-9])

That is, just use [A-Za-z0-9] to represent the final of 63 possible characters in the pattern.

edited Sep 13 '21 at 10:04

answered Sep 13 '21 at 09:39

Tim Biegeleisen

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The issue with this regex (which the original regex accounts for), is the following cases are not matched : [email protected] [email protected] [email protected] [email protected] – user3055126 Sep 13 '21 at 09:54
My answer should be logically _equivalent_ to what you have above, and it should fully address the incompatibility issue. If you have some _other_ issue with your current regex, you might want to open a new question. – Tim Biegeleisen Sep 13 '21 at 09:58
Can you please explain how it is logically equivalent if the original regex matched certain emails that the new regex you provided isn't ? – user3055126 Sep 13 '21 at 10:00
1

@user3055126 You were right, I had a problem. Please try the update above. – Tim Biegeleisen Sep 13 '21 at 10:04

score 0 · Answer 2 · answered Sep 13 '21 at 11:40

This regex will not work likely problem in regex pattern i think.

this works for me for simple email format [email protected]

var regex = /^(([^<>()\[\]\\.,;:\s@"]+(\.[^<>()\[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;

Regex - unhandled js exception in react native

2 Answers2