A react native module that lets you to register a global error handler

import {setJSExceptionHandler, getJSExceptionHandler} from 'react-native-exception-handler';

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// registering the error handler (maybe u can do this in the index.android.js or index.ios.js)
setJSExceptionHandler((error, isFatal) => {
  // This is your custom global error handler
  // You do stuff like show an error dialog
  // or hit google analytics to track crashes
  // or hit a custom api to inform the dev team.
});

// getJSExceptionHandler gives the currently set JS exception handler
const currentHandler = getJSExceptionHandler();

import {setNativeExceptionHandler} from 'react-native-exception-handler';

setNativeExceptionHandler((exceptionString) => {
  // This is your custom global error handler
  // You do stuff likehit google analytics to track crashes.
  // or hit a custom api to inform the dev team.
  //NOTE: alert or showing any UI change via JS
  //WILL NOT WORK in case of NATIVE ERRORS.
});

const errorHandler = (error, isFatal) => {
  // This is your custom global error handler
  // You do stuff like show an error dialog
  // or hit google analytics to track crashes
  // or hit a custom api to inform the dev team.
})
//Second argument is a boolean with a default value of false if unspecified.
//If set to true the handler to be called in place of RED screen
//in development mode also.
setJSExceptionHandler(errorHandler, true);

import com.masteratul.exceptionhandler.ReactNativeExceptionHandlerModule;
import <yourpackage>.YourCustomActivity; //This is your CustomErrorDialog.java
...
...
...
public class MainApplication extends Application implements ReactApplication {
...
...
  @Override
  public void onCreate() {
    ....
    ....
    ....
    ReactNativeExceptionHandlerModule.replaceErrorScreenActivityClass(YourCustomActivity.class); //This will replace the native error handler popup with your own custom activity.
  }

#import "AppDelegate.h"

#import <React/RCTBundleURLProvider.h>
#import <React/RCTRootView.h>

//Add the header file
#import "ReactNativeExceptionHandler.h"
...
...
@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
...
...

[ReactNativeExceptionHandler replaceNativeExceptionHandlerBlock:^(NSException *exception, NSString *readeableException){

    // THE CODE YOU WRITE HERE WILL REPLACE THE EXISTING NATIVE POPUP THAT COMES WITH THIS MODULE.
    //We create an alert box
    UIAlertController* alert = [UIAlertController
                                alertControllerWithTitle:@"Critical error occurred"
                                message: [NSString stringWithFormat:@"%@\n%@",
                                          @"Apologies..The app will close now \nPlease restart the app\n",
                                          readeableException]
                                preferredStyle:UIAlertControllerStyleAlert];

    // We show the alert box using the rootViewController
    [rootViewController presentViewController:alert animated:YES completion:nil];

    // THIS IS THE IMPORTANT PART
    // By default when an exception is raised we will show an alert box as per our code.
    // But since our buttons wont work because our click handlers wont work.
    // to close the app or to remove the UI lockup on exception.
    // we need to call this method
    // [ReactNativeExceptionHandler releaseExceptionHold]; // to release the lock and let the app crash.

    // Hence we set a timer of 4 secs and then call the method releaseExceptionHold to quit the app after
    // 4 secs of showing the popup
    [NSTimer scheduledTimerWithTimeInterval:4.0
                                     target:[ReactNativeExceptionHandler class]
                                   selector:@selector(releaseExceptionHold)
                                   userInfo:nil
                                    repeats:NO];

    // or  you can call
    // [ReactNativeExceptionHandler releaseExceptionHold]; when you are done to release the UI lock.
  }];

...
...
...

 return YES;
}

@end

[NSTimer scheduledTimerWithTimeInterval:4.0
                                 target:[ReactNativeExceptionHandler class]
                               selector:@selector(releaseExceptionHold)
                               userInfo:nil
                                repeats:NO];

import {Alert} from 'react-native';
import RNRestart from 'react-native-restart';
import {setJSExceptionHandler} from 'react-native-exception-handler';

const errorHandler = (e, isFatal) => {
  if (isFatal) {
    Alert.alert(
        'Unexpected error occurred',
        `
        Error: ${(isFatal) ? 'Fatal:' : ''} ${e.name} ${e.message}

        We will need to restart the app.
        `,
      [{
        text: 'Restart',
        onPress: () => {
          RNRestart.Restart();
        }
      }]
    );
  } else {
    console.log(e); // So that we can see it in the ADB logs in case of Android if needed
  }
};

setJSExceptionHandler(errorHandler);

setNativeExceptionHandler((errorString) => {
    //You can do something like call an api to report to dev team here
    ...
    ...
   // When you call setNativeExceptionHandler, react-native-exception-handler sets a  
   // Native Exception Handler popup which supports restart on error in case of android.
   // In case of iOS, it is not possible to restart the app programmatically, so we just show an error popup and close the app.
   // To customize the popup screen take a look at CUSTOMIZATION section.
});

import {Alert} from 'react-native';
import {BackAndroid} from 'react-native';
import {setJSExceptionHandler} from 'react-native-exception-handler';

const reporter = (error) => {
  // Logic for reporting to devs
  // Example : Log issues to github issues using github apis.
  console.log(error); // sample
};

const errorHandler = (e, isFatal) => {
  if (isFatal) {
    reporter(e);
    Alert.alert(
        'Unexpected error occurred',
        `
        Error: ${(isFatal) ? 'Fatal:' : ''} ${e.name} ${e.message}

        We have reported this to our team ! Please close the app and start again!
        `,
      [{
        text: 'Close',
        onPress: () => {
          BackAndroid.exitApp();
        }
      }]
    );
  } else {
    console.log(e); // So that we can see it in the ADB logs in case of Android if needed
  }
};

setJSExceptionHandler(errorHandler);

setNativeExceptionHandler((errorString) => {
    //You can do something like call an api to report to dev team here
    //example
    // fetch('http://<YOUR API TO REPORT TO DEV TEAM>?error='+errorString);
    //
});