Array sort with comparator works with remote debugging on but doesn't work with it off

[FrickenHamster]

• Review the documentation: https://facebook.github.io/react-native
• Search for existing issues: https://github.com/facebook/react-native/issues
• Use the latest React Native release: https://github.com/facebook/react-native/releases

Environment

React Native Environment Info:
System:
OS: Windows 7
CPU: x64 Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz
Memory: 18.15 GB / 31.89 GB
Binaries:
Yarn: yarn install v0.21.3
info No lockfile found.
[1/4] Resolving packages...
[2/4] Fetching packages...
info "fsevents@1.2.4" is an optional dependency and failed compatibility check. Excluding it from installation.
[3/4] Linking dependencies...
[4/4] Building fresh packages...
success Saved lockfile.
Done in 58.85s. - ~\AppData\Roaming\npm\yarn.CMD
npm: 5.4.2 - C:\Program Files\nodejs\npm.CMD
IDEs:
Android Studio: Version 3.2.0.0 AI-181.5540.7.32.5014246

I am running RN 0.57

Description

It seems if you are running on an android device, I've tested on the emulator and my physical devices and you call sort on an array with a comparator function ie:
const a = [4,6,2,3]; a.sort((a, b) => a > b); Alert.alert(a.join(','))

If you are remote debugging, it'll run correctly and output 2,3,4,6

However, if you are not remote debugging, it'll output 4,6,2,3

Reproducible Demo

In any react native project, make a button and in the callback have it run something like
const a = [4,6,2,3]; a.sort((a, b) => a > b); Alert.alert(a.join(','))

[FrickenHamster]

After some help from a guy in discord and thinking, I've discovered the problem is because debug mode uses chrome's js engine, which accepts truthy values from the comparator function, while the default react native engine only accepts numbers.
Thus I was able to fix it by appending a ? 1 : -1 after each truthy statement.
Imo this behavior should be fixed to be consistent between debug and non debug mode, but I don't know if it is possible.

[zibs]

Yep this is a semi well known issue that definitely catches most people at least once - there is some talk about upgrading the Android JSC here and elsewhere: https://github.com/react-community/jsc-android-buildscripts

[kelset]

Yes, this issue has been reported already - please refer to #19737