React Native DEV and PROD variables

You can use the __DEV__ variable. By default if you run your app with npx react-native run-ios or npx react-native run-android, it will run in Debug mode and __DEV__ will be true. In release mode, __DEV__ will be false. You can use it this way:

const CLOUD_API_BASE_URL = __DEV__ ? 'https://api-dev.yourdomain.com' : 'https://api-prod.yourdomain.com';

You can run the app in Release mode with the terminal: react-native run-android --variant release #android react-native run-ios --configuration Release #ios

Or open the ios folder in XCode, choose Product > Scheme > Edit Schemes Select Run in the left menu. For Build Configuration, choose 'Release' and uncheck 'Debug executable'

In Android Studio, similarly, you can set the build variant to release

You can use the __DEV__ global variable in JavaScript to determine if you're using React Native packager or not. If you are running your app in the iOS Simulator or Android emulator __DEV__ will be set to true.

https://reactnative.dev/docs/javascript-environment

When the __DEV__ variable is set to true, it turns on a bunch of useful development warnings. For production, it is recommended to set __DEV__=false.