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 — Muhammad Usama Ashraf
– Muhammad Usama Ashraf, Commented Sep 13, 2021 at 9:39

Tim Biegeleisen · Accepted Answer · 2021-09-13 10:04:43Z

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, 2021 at 10:04

answered Sep 13, 2021 at 9:39

Tim Biegeleisen

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4 Comments

user3055126 Over a year ago

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]

Tim Biegeleisen Over a year ago

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.

user3055126 Over a year ago

Can you please explain how it is logically equivalent if the original regex matched certain emails that the new regex you provided isn't ?

Tim Biegeleisen Over a year ago

@user3055126 You were right, I had a problem. Please try the update above.

vivaan · Accepted Answer · 2021-09-13 11:40:10Z

0

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,}))$/;

answered Sep 13, 2021 at 11:40

vivaan

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