BackHandler

import { BackHandler } from 'react-native';

static addEventListener(
  eventName: 'hardwareBackPress',
  handler: () => boolean | null | undefined
): { remove: () => void }

import React, { useEffect } from 'react';
import { BackHandler } from 'react-native';

function MyComponent() {
  useEffect(() => {
    const backHandler = BackHandler.addEventListener(
      'hardwareBackPress',
      () => {
        // Handle back button press
        // Return true to prevent default behavior (exit app)
        // Return false to let default behavior happen
        if (shouldPreventBack) {
          // Do something
          return true;
        }
        return false;
      }
    );

    return () => backHandler.remove();
  }, []);

  return null;
}

static exitApp(): void

import { BackHandler } from 'react-native';

BackHandler.exitApp();

import React, { useEffect } from 'react';
import { BackHandler, Alert } from 'react-native';

function App() {
  useEffect(() => {
    const backAction = () => {
      Alert.alert('Hold on!', 'Are you sure you want to exit?', [
        {
          text: 'Cancel',
          onPress: () => null,
          style: 'cancel',
        },
        { text: 'YES', onPress: () => BackHandler.exitApp() },
      ]);
      return true;
    };

    const backHandler = BackHandler.addEventListener(
      'hardwareBackPress',
      backAction
    );

    return () => backHandler.remove();
  }, []);

  return (
    // Your app content
  );
}