How can I use Firebase Functions to send FCM to user?
Solution 1:
Firebase SDK for Cloud Functions includes the Firebase Admin SDK, you can find an example that we made here Send Firebase Cloud Messaging notifications for new followers
In brief:
const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);
exports.foo = functions.database.ref('/bar').onWrite(event => {
const tokens = ...;
const payload = ...;
return admin.messaging().sendToDevice(tokens, payload);
})