react native is not excepting positive/negative lookbehinds as valid regex

[SyntappZ]

Description

in my app when trying to use positive/negative lookbehinds i get this error: invalid regular expression invalid group specifier name my main app is on react native 62 i have made an app for testing purposes and this is on the latest react native 63.4 and the error still persists, i think this is a bug but if not any help or advice on how to fix this would be greatly appreciated.

React Native version:

System: OS: Windows 10 10.0.19041 CPU: (8) x64 Intel(R) Core(TM) i7-4790K CPU @ 4.00GHz Memory: 11.31 GB / 15.94 GB Binaries: Node: 12.18.2 - C:\Program Files\nodejs\node.EXE Yarn: Not Found npm: 6.14.11 - C:\Program Files\nodejs\npm.CMD Watchman: Not Found SDKs: Android SDK: API Levels: 23, 26, 28, 29, 30 Build Tools: 28.0.3, 29.0.2, 29.0.3, 30.0.1 System Images: android-23 | Google APIs Intel x86 Atom, android-25 | Google Play Intel x86 Atom, android-27 | Google APIs Intel x86 Atom, android-27 | Google Play Intel x86 Atom, android-28 | Google APIs Intel x86 Atom_64 Android NDK: Not Found Windows SDK: Not Found IDEs: Android Studio: Not Found Visual Studio: Not Found Languages: Java: 1.8.0_271 - /c/Program Files/Java/jdk1.8.0_271/bin/javac Python: 2.7.3 - /c/Python27/python npmPackages: @react-native-community/cli: Not Found react: 16.13.1 => 16.13.1 react-native: 0.63.4 => 0.63.4 react-native-windows: Not Found npmGlobalPackages: react-native: Not Found

Steps To Reproduce

I have added a test app repo for testing. i have added 9 test buttons and only the lookbehinds fail.

1. press the quick test buttons for a quick test or type your own regex in the input to test.
2. to get the error and call stack turn off the safety switch.

Expected Results

I expected for the regex to be valid

Snack, code example, screenshot, or link to a repository:

testing repo - https://github.com/SyntappZ/react-native-regex-testing

[safaiyeh]

@SyntappZ Thank you for the repo example! Great UI on it.

It seems weird that a valid regex expression does not validate correctly on React Native. This is definitely an issue, nice catch. Added the appropriate labels

[SyntappZ]

@safaiyeh Thanks mate 🙂

[saurabhbh21]

Is there any update on this. I'm facing the same issue is react native version 0.68.2.

[saurabhbh21]

The issue is lookbehind regex is not supported in JSC (which is JS compiler in RN). Replacing JSC with Hermes fixed the issue for me.