This sample demonstrates how to send a Firebase Cloud Messaging (FCM) notification from a Realtime Database triggered Function. The sample also features a Web UI to experience the FCM notification.

See file functions/index.js for the code.

Sending the notification is done using the Firebase Admin SDK . The Web client writes the individual device tokens to the realtime database which the Function uses to send the notification.

The dependencies are listed in functions/package.json .

Users sign into the app and are requested to enable notifications on their browsers. If they successfully enable notifications the device token is saved into the datastore under /users/$uid/notificationTokens .:

/functions-project-12345
    /users
        /Uid-12345
            displayName: "Bob Dole"
            /notificationTokens
                1234567890: true
            photoURL: "https://lh3.googleusercontent.com/..."

If a user starts following another user we'll write to /followers/$followedUid/$followerUid :

/functions-project-12345
    /followers
        /followedUid-12345
            followerUid-67890: true
    /users
        /Uid-12345
            displayName: "Bob Dole"
            /notificationTokens
                1234567890: true
            photoURL: "https://lh3.googleusercontent.com/..."

The function triggers every time the value of a follow flag changes at /followers/$followedUid/$followerUid .

This sample comes with a web-based UI for testing the function. To test it out:

1. Set up your Firebase project:
   1. Create a Firebase project
   2. Register your web app with Firebase
2. Enable Google Provider in the Auth section
3. Clone or download this repo and open the fcm-notification directory.
4. You must have the Firebase CLI installed. If you don't have it install it with npm install -g firebase-tools and then configure it with firebase login .
5. Configure the CLI locally by using firebase use --add and select your project in the list.
6. Install dependencies locally by running: cd functions; npm install; cd -
7. Deploy your project using firebase deploy
8. Open the app using firebase open hosting:site , this will open a browser.
9. Start following a user, this will send a notification to him.