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How do I know if my React Native app is running in production or development? Is there some sort of way within JavaScript to tell? Is there a global that is passed in?

Ryan McDermott
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  • FYI, I was getting this when importing a Component in `react-native` in my `globalSetup` file. Moving this setup from `globalSetup` to `setupFilesAfterEnv` did the trick, since the `jest` test environment is loaded before the files listed in `setupFilesAfterEnv` are run. – Joshua Pinter May 25 '21 at 21:22

4 Answers4

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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

Community
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Austin
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    Also if you are running the app on a physical device using `react-native run-*` – Ricardo Stuven Aug 13 '16 at 17:17
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    What about when you run in a simulator with `--configuration Release`? Does this still use the React Native packager and set `__DEV__` to `true`? – Marklar Nov 16 '18 at 04:46
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    @Marklar when running in release configuration, the `__DEV__` is NOT set to true in my experience. – Tope Apr 09 '19 at 12:24
  • `__DEV__` is only about the build configuration. If you want to detect whether the app is running on device or in a simulator, use something like `react-native-device-info`. – Tamlyn May 24 '23 at 10:54
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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 xcode edit scheme Select Run in the left menu. For Build Configuration, choose 'Release' and uncheck 'Debug executable'

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In Android Studio, similarly, you can set the build variant to release enter image description here

Raphael Pinel
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    what if I have multiple variant (uat , sit, prod ) and not just simple (debug or release) , I want to know exactly where is that piece of toggle in build gradle turning __DEV__ true or false , i cannot find any resource telling me to do this – elliotching Apr 12 '22 at 09:24
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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.

Abhishek Kumar
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I didn't intend to write an answer, but I'm not able to comment (<50 pts). To toggle __DEV__, you can set it before your command, e.g.:

__DEV__=true expo start (should already be set to true though)

or

__DEV__=false react-native run-ios (should be set to true by default, when running this command without setting manually)

stereoplegic
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