Firebase and express barebone.

express-and-firebase.js

'use strict';

// [START import]
const functions = require('firebase-functions');
const express = require('express');
const app = express();
// [END import]

// [START middleware]
const cors = require('cors')({origin: true});
app.use(cors);
// [END middleware]


// Define the Firebase function that will act as Express application
// Note: This `api` must match with `/firebase.json` rewrites rule.
exports.api = functions.https.onRequest(app);