How to send email verification after user creation with Firebase Cloud functions?

Question

I\'m trying to send the verification email after the user is created. Since there\'s no way on Firebase itself, I\'m trying it with cloud functions.

I cannot really

Answer 1

This is how I implemented it successfully using Firebase cloud functions along with a small express backend server

Firebase Cloud function (background) triggered with every new user created

• This function sends a "user" object to your api endpoint

const functions = require('firebase-functions');
const fetch = require('node-fetch');

// Send email verification through express server
exports.sendVerificationEmail = functions.auth.user().onCreate((user) => {
  // Example of API ENPOINT URL 'https://mybackendapi.com/api/verifyemail/'
  return fetch( < API ENDPOINT URL > , {
      method: 'POST',
      body: JSON.stringify({
        user: user
      }),
      headers: {
        "Content-Type": "application/json"
      }
    }).then(res => console.log(res))
    .catch(err => console.log(err));
});

Server Middleware code

• verifyEmail here is used as middleware

// File name 'middleware.js'
import firebase from 'firebase';
import admin from 'firebase-admin';

// Get Service account file from firebase console
// Store it locally - make sure not to commit it to GIT
const serviceAccount = require('');
// Get if from Firebase console and either use environment variables or copy and paste them directly
// review security issues for the second approach
const config = {
  apiKey: process.env.APIKEY,
  authDomain: process.env.AUTHDOMAIN,
  projectId: process.env.PROJECT_ID,
};
// Initialize Firebase Admin
admin.initializeApp({
  credential: admin.credential.cert(serviceAccount),
});

// Initialize firebase Client
firebase.initializeApp(config);

export const verifyEmail = async(req, res, next) => {
  const sentUser = req.body.user;
  try {
    const customToken = await admin.auth().createCustomToken(sentUser.uid);
    await firebase.auth().signInWithCustomToken(customToken);
    const mycurrentUser = firebase.auth().currentUser;
    await mycurrentUser.sendEmailVerification();
    res.locals.data = mycurrentUser;
    next();
  } catch (err) {
    next(err);
  }
};

Server code

// Filename 'app.js'
import express from 'express';
import bodyParser from 'body-parser';
// If you don't use cors, the api will reject request if u call it from Cloud functions
import cors from 'cors';
import {
  verifyEmail
} from './middleware'

app.use(cors());
app.use(bodyParser.urlencoded({
  extended: true,
}));
app.use(bodyParser.json());

const app = express();
// If you use the above example for endpoint then here will be
// '/api/verifyemail/'
app.post('', verifyEmail, (req, res, next) => {
  res.json({
    status: 'success',
    data: res.locals.data
  });
  next()
})

This endpoint will return back the full user object and will send the verification email to user.

I hope this helps.