We use Firebase for authentication in our web apps, and I've built an API proxy to retrieve all the authenticated users from Firebase.

1. You need Firebase service account json file. Login into your Firebase Project Account, Go to Project settings → Services Accounts → Generate new private key. Save that json file in a folder in app/files.

2. Install the firebase SDK package.

terminal
Copy
npm install firebase-admin

3. Open server.js file and add two lines in this file.

JavaScript
Copy
// server.js
const firebaseProxyRoutes = require('./app/routes/firebaseProxyRoutes');

app.use('/firebase/proxy', firebaseProxyRoutes);

4. Create a route file in the app/routes directory named firebaseProxyRoutes.js

JavaScript
Copy
// app/routes/firebaseProxyRoutes.js
const express = require('express');
const router = express.Router();
const firebaseController = require('../controllers/firebaseController');

router.get('/auth/users', firebaseController.authUsers);

module.exports = router;

5. Create a controller file in the app/controllers directory named firebaseController.js

JavaScript
Copy
// app/controllers/firebaseController.js
const { responseList } = require('../errors/responseList');
const admin = require('firebase-admin');
const serviceAccount = require('path/to/firebase-adminsdk-private-key.json');

// Initialize Firebase Admin SDK
admin.initializeApp({
    credential: admin.credential.cert(serviceAccount),
});

const auth = admin.auth();

// List firebase auth users
exports.authUsers = async (req, res) => {
    const { limit, pageToken } = req.query;
    try {
        let listUsersResult;
        if (pageToken) {
            listUsersResult = await auth.listUsers(limit || 100, pageToken);
        } else {
            listUsersResult = await auth.listUsers(limit || 100);
        }

        const users = listUsersResult.users.map((userRecord) =>
            userRecord.toJSON()
        );
        res.status(200).send({ users, pageToken: listUsersResult.pageToken });
    } catch (error) {
        res.status(500).send(responseList(500, error.message));
    }
};

Now the API is ready to get Firebase Auth Users as JSON.

Copy
http://localhost:3001/firebase/proxy/auth/user