The Mysterious Case of “ReferenceError: ‘BigInt’ doesn’t exist (Hermes); Invariant Violation: AppRegistry module not registered (Hermes)”

Are you tired of seeing those cryptic error messages in your React Native app? You know, the ones that leave you scratching your head, wondering what on earth went wrong. Well, fear not, dear developer! In this article, we’ll delve into the mysterious world of “ReferenceError: ‘BigInt’ doesn’t exist (Hermes); Invariant Violation: AppRegistry module not registered (Hermes)” and uncover the secrets to fixing this pesky issue.

What is Hermes and Why is it Causing Issues?

Hermes is a JavaScript engine developed by Facebook, designed to improve the performance of React Native apps. It’s enabled by default in newer versions of React Native, so it’s likely you’re using it without even realizing it. However, with great power comes great responsibility, and sometimes Hermes can be a bit finicky. That’s where our error comes in.

The Error Message: A Closer Look

Let’s break down the error message and understand what’s going on:

ReferenceError: 'BigInt' doesn't exist (Hermes);
Invariant Violation: AppRegistry module not registered (Hermes)

The first part of the error message, “ReferenceError: ‘BigInt’ doesn’t exist (Hermes)”, tells us that Hermes is complaining about the absence of the BigInt type. BigInt is a new numeric type in JavaScript that allows for arbitrary-precision integers. It’s a fancy way of saying “really big numbers”. Hermes is trying to use BigInt, but it can’t find it.

The second part, “Invariant Violation: AppRegistry module not registered (Hermes)”, suggests that there’s an issue with the AppRegistry module, which is a critical component of React Native. AppRegistry is responsible for registering and managing the app’s components. In this case, it seems that the module hasn’t been registered properly.

Solutions to the Error: A Step-by-Step Guide

Don’t worry, we’ve got you covered! Here are the steps to fix this error and get your app up and running again:

Step 1: Check Your React Native Version

Make sure you’re running the latest version of React Native. You can check by running:

npx react-native --version

If you’re not on the latest version, update using:

npx react-native upgrade

Step 2: Enable Hermes in Your App

Double-check that Hermes is enabled in your app. You can do this by adding the following line to your `android/app/src/main/java/com/yourcompany/MainActivity.java` file:

import com.facebook.hermes.reactexecutor.HermesExecutorFactory;
...
public class MainActivity extends AppCompatActivity {
  ...
  protected ReactActivityDelegate createReactActivityDelegate() {
    return new ReactActivityDelegate(this, getMainComponentName(), enableHermes ? new HermesExecutorFactory() : null);
  }
  ...
}

Alternatively, you can enable Hermes in your `Info.plist` file (for iOS) by adding:

<key>EnableHermes</key>
<true/>

Step 3: Register the AppRegistry Module

Ensure that the AppRegistry module is registered properly in your app. You can do this by adding the following line to your `index.js` file:

import { AppRegistry } from 'react-native';
...
AppRegistry.registerComponent('App', () => App);

Step 4: Fix BigInt Issues

If you’re still encountering issues with BigInt, try adding the following line to your `babel.config.js` file:

module.exports = {
  ...
  plugins: [
    ['@babel/plugin-transform-bigint', { loose: true }],
  ],
};

This will enable the BigInt plugin in Babel, which should fix any BigInt-related issues.

Step 5: Clean and Rebuild Your App

Finally, clean and rebuild your app to ensure that all changes take effect:

npx react-native run-android --clean
npx react-native run-ios --clean

And that’s it! You should now be able to run your app without encountering the dreaded “ReferenceError: ‘BigInt’ doesn’t exist (Hermes); Invariant Violation: AppRegistry module not registered (Hermes)” error.

Common Pitfalls and Troubleshooting Tips

Here are some common pitfalls and troubleshooting tips to keep in mind:

• Make sure you’ve enabled Hermes in your app, as outlined in Step 2.
• Double-check that the AppRegistry module is registered properly, as shown in Step 3.
• If you’re still encountering issues with BigInt, try updating your Babel version or using a different BigInt plugin.
• If none of the above steps work, try resetting your React Native project by running `npx react-native init ` and reconfiguring your project from scratch.

Conclusion

And there you have it, folks! With these steps, you should be able to fix the “ReferenceError: ‘BigInt’ doesn’t exist (Hermes); Invariant Violation: AppRegistry module not registered (Hermes)” error and get your React Native app up and running again. Remember to stay vigilant, keep your React Native version up to date, and don’t be afraid to reach out for help if you encounter any further issues.

Troubleshooting Tip	Fix
Hermes not enabled	Enable Hermes in your app
AppRegistry module not registered	Register the AppRegistry module in your index.js file
BigInt issues	Enable the BigInt plugin in Babel
App not building	Clean and rebuild your app

Related Errors and Exceptions

If you’re still encountering issues, here are some related errors and exceptions to look out for:

• ReferenceError: Can’t find variable: Intl (Hermes)
• Invariant Violation: Module AppRegistry is not a registered callable module (Hermes)
• Error: Unable to resolve module ./node_modules/react-native/Libraries/Core/InitializeCore.js (Hermes)

Remember, these errors often have similar solutions, so try applying the steps outlined above to fix these issues as well.

Final Thoughts

The “ReferenceError: ‘BigInt’ doesn’t exist (Hermes); Invariant Violation: AppRegistry module not registered (Hermes)” error can be frustrating, but with these steps and troubleshooting tips, you should be able to fix it and get your app running smoothly. Happy coding, and don’t hesitate to reach out if you need further assistance!

Word count: 1050

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