Why is sendMulticast() missing in Firebase Admin's Messaging for Node.js?

It looks like your Firebase Admin SDK version doesn’t support the sendMulticast() method. In recent versions (v9.0.0 and above) of the Firebase Admin SDK for Node.js, the Messaging API includes sendMulticast(), which is designed to send a MulticastMessage to multiple registration tokens.

To resolve the issue, you have two options:

1. Upgrade the Firebase Admin SDK:
   Update your firebase-admin package to the latest version (or at least v9.0.0 or later) by running:

   BASHCopied
   npm install firebase-admin@latest

   This should expose the sendMulticast() method on the Messaging instance.

2. Fallback to sending messages individually:
   If for some reason you cannot upgrade, you’ll need to send notifications to each token one by one, perhaps using Promise.all() to send them concurrently. For example:

   JAVASCRIPTCopied
   const tokens = multicastMessage.tokens; // Array of registration tokens
   const message = { ...multicastMessage, token: undefined }; // Remove tokens property
   
   const sendMessages = tokens.map(token => {
     return messaging().send({ ...message, token });
   });
   
   const responses = await Promise.all(sendMessages);
   console.log('Successfully sent messages:', responses);

By upgrading the SDK, you get the benefit of the sendMulticast() method which handles batching (up to 500 tokens per request) internally. Make sure to check the Firebase Admin SDK release notes and documentation for any additional configuration or breaking changes if you do upgrade.

If you have further questions on implementing FCM features, feel free to ask!