React Native - __DEV__ is not defined

ghz 6months ago ⋅ 67 views

I have a react-native@0.26.2 project. I have deleted the node_modules folder and after i have given the following commands:

npm i
react-native upgrade

but I get this error:

react-native.js:15 

ReferenceError: __DEV__ is not defined

How do I fix?

Answers

The error you're encountering, ReferenceError: __DEV__ is not defined, typically occurs in React Native projects when the global variable __DEV__ is not correctly defined or accessible. This variable is usually defined by Metro bundler (formerly known as Metro bundler, formerly known as React Packager) during development to differentiate between development and production environments.

Here’s how you can troubleshoot and resolve this issue:

1. Verify Metro Bundler Configuration

First, ensure that your Metro bundler configuration is correctly set up. React Native projects rely on Metro to bundle JavaScript files, and __DEV__ is one of the variables it provides.

  • Check Metro Configuration: Look for any custom Metro configuration files (metro.config.js or metro.config.json) in your project. Ensure they are correctly set up or try using the default configuration.

2. Check React Native Version Compatibility

React Native 0.26.2 is quite an old version, and newer versions of Metro might have changes that affect compatibility. Consider upgrading to a more recent version of React Native if possible (react-native upgrade might not upgrade you to the latest version).

3. Clean Cache and Reinstall Dependencies

Sometimes, issues like these can stem from cached files or incomplete installations. Follow these steps to clean up and reinstall dependencies:

  • Clean Cache:

    npm start -- --reset-cache

  • Reinstall Dependencies:

    rm -rf node_modules/
npm install

  • Check npm Packages: Ensure all dependencies are correctly installed and compatible with React Native 0.26.2.

4. Ensure Environment Setup

Make sure your development environment (IDE, CLI tools) is properly configured and up to date. This includes Node.js, npm, and any other tools necessary for React Native development.

5. Review Project-specific Changes

If your project has any customizations or changes that affect Metro’s behavior, review those changes carefully. Sometimes, modifications to Metro configurations or build scripts can inadvertently cause issues like __DEV__ not being defined.

6. Upgrade React Native (if possible)

Consider upgrading to a newer version of React Native that might have better compatibility with newer versions of Metro and other dependencies.

Additional Notes

  • Documentation: Check the React Native documentation for the specific version you are using. There might be version-specific notes or troubleshooting tips.
  • Community Support: Utilize forums, GitHub issues, or community resources specific to React Native for further assistance.

By following these steps, you should be able to resolve the ReferenceError: __DEV__ is not defined issue and continue with your React Native development smoothly. If problems persist, consider reaching out to the React Native community or forums for more tailored assistance.

#javascript