Firebase Cloud Messaging vs OneSignal

import { initializeApp } from 'firebase-admin/app';
import { getMessaging } from 'firebase-admin/messaging';

initializeApp({
  credential: cert({
    projectId: process.env.FIREBASE_PROJECT_ID!,
    clientEmail: process.env.FIREBASE_CLIENT_EMAIL!,
    privateKey: process.env.FIREBASE_PRIVATE_KEY!.replace(/\\n/g, '\n'),
  }),
});

// Send a notification to a single device
const message = {
  notification: {
    title: 'New message',
    body: 'You have a new message from Alice',
  },
  token: 'device_fcm_token_here',
};

const response = await getMessaging().send(message);
console.log('Successfully sent:', response);

import * as OneSignal from '@onesignal/node-onesignal';

const config = OneSignal.createConfiguration({
  restApiKey: process.env.ONESIGNAL_API_KEY!,
});
const client = new OneSignal.DefaultApi(config);

// Send a push notification to all subscribers
const notification = new OneSignal.Notification();
notification.app_id = process.env.ONESIGNAL_APP_ID!;
notification.contents = { en: 'Your order has shipped!' };
notification.headings = { en: 'Order Update' };
notification.included_segments = ['All'];

const response = await client.createNotification(notification);
console.log('Notification ID:', response.id);