Simple Firebase trigger Function to send a Twilio SMS

index.js

// index.js for Firebase Functions
// SMS is triggered when an alert object is added to the alert queue path

const functions = require('firebase-functions');
const admin = require('firebase-admin');
const twilio = require('twilio');

admin.initializeApp(functions.config().firebase);
const db = admin.database();

const ALERT_QUEUE_PATH = '/alerts/queue'; // objects stored here trigger SMS

// Firebase trigger Function to send an SMS
exports.watchAlertQueue = functions.database.ref(`${ALERT_QUEUE_PATH}/{ALERT}`).onWrite(
  (event) => new Promise((resolve, reject) => {
    // on trigger, an event is passed in
    // event.data.val() will be a single object, 
    // because we included a wildcard in the watched path, {ALERT}
    // we return a Promise because this Function makes asynchronous calls
    const alert = event.data.val(); 
    const message = alert.alertText; // text for SMS contained in alertText property
    const client = new twilio.RestClient(accountSid, authToken); // TODO: Add values for your Twilio account

    client.messages.create({
      to: MY_NUMBER, // TODO: add destination number
      from: TWILIO_NUMBER, // TODO: add your Twilio outbound number
      body: message,
    }, (err) => {
      if (err) {
        // didn't go through, let's fulfill promise with a rejection
        console.error(err.message);
        return reject();
      }
      // success -- let's record this, then remove the alert from the queue
      const ALERT_RECORD_PATH = '/alerts/records';
      db.ref(`${ALERT_RECORD_PATH}/${alert.GUID}`).set(alert).then(() => {
        db.ref(`${ALERT_QUEUE_PATH}/${alert.GUID}`).remove().then(() => 
          resolve()).catch(() => reject());
        }).catch(() => reject());
      });
    })
);