Firebase Buddy

Common Firebase patterns without the complexity.

Quick Setup Checklist

1. Install Firebase:

   npm install firebase

2. Create config file (lib/firebase.js or firebase.ts):

   import { initializeApp } from 'firebase/app';
   import { getFirestore } from 'firebase/firestore';
   import { getAuth } from 'firebase/auth';
   import { getStorage } from 'firebase/storage';
   
   const firebaseConfig = {
     apiKey: process.env.NEXT_PUBLIC_FIREBASE_API_KEY,
     authDomain: process.env.NEXT_PUBLIC_FIREBASE_AUTH_DOMAIN,
     projectId: process.env.NEXT_PUBLIC_FIREBASE_PROJECT_ID,
     storageBucket: process.env.NEXT_PUBLIC_FIREBASE_STORAGE_BUCKET,
     messagingSenderId: process.env.NEXT_PUBLIC_FIREBASE_MESSAGING_SENDER_ID,
     appId: process.env.NEXT_PUBLIC_FIREBASE_APP_ID,
   };
   
   const app = initializeApp(firebaseConfig);
   export const db = getFirestore(app);
   export const auth = getAuth(app);
   export const storage = getStorage(app);

3. Create .env.local:

   NEXT_PUBLIC_FIREBASE_API_KEY=your-key
   NEXT_PUBLIC_FIREBASE_AUTH_DOMAIN=your-project.firebaseapp.com
   NEXT_PUBLIC_FIREBASE_PROJECT_ID=your-project
   NEXT_PUBLIC_FIREBASE_STORAGE_BUCKET=your-project.appspot.com
   NEXT_PUBLIC_FIREBASE_MESSAGING_SENDER_ID=123456
   NEXT_PUBLIC_FIREBASE_APP_ID=1:123:web:abc

Firestore Patterns

Read Data

import { doc, getDoc, collection, getDocs, query, where, orderBy, limit } from 'firebase/firestore';
import { db } from './firebase';

// Get one document
const docSnap = await getDoc(doc(db, 'users', 'userId'));
if (docSnap.exists()) {
  console.log(docSnap.data());
}

// Get all documents in collection
const querySnapshot = await getDocs(collection(db, 'users'));
querySnapshot.forEach((doc) => {
  console.log(doc.id, doc.data());
});

// Query with filters
const q = query(
  collection(db, 'posts'),
  where('author', '==', 'userId'),
  orderBy('createdAt', 'desc'),
  limit(10)
);
const results = await getDocs(q);

Write Data

import { doc, setDoc, addDoc, updateDoc, deleteDoc, collection, serverTimestamp } from 'firebase/firestore';
import { db } from './firebase';

// Set with specific ID
await setDoc(doc(db, 'users', 'userId'), {
  name: 'John',
  email: 'john@example.com',
  createdAt: serverTimestamp()
});

// Add with auto-generated ID
const docRef = await addDoc(collection(db, 'users'), {
  name: 'Jane',
  email: 'jane@example.com'
});
console.log('New doc ID:', docRef.id);

// Update specific fields
await updateDoc(doc(db, 'users', 'userId'), {
  name: 'John Updated'
});

// Delete
await deleteDoc(doc(db, 'users', 'userId'));

Real-time Listener

import { doc, collection, onSnapshot, query, where } from 'firebase/firestore';
import { db } from './firebase';

// Listen to one document
const unsubscribe = onSnapshot(doc(db, 'users', 'userId'), (doc) => {
  console.log('Current data:', doc.data());
});

// Listen to collection with query
const q = query(collection(db, 'messages'), where('roomId', '==', 'room1'));
const unsubscribe = onSnapshot(q, (snapshot) => {
  snapshot.forEach((doc) => {
    console.log(doc.data());
  });
});

// Call unsubscribe() to stop listening (important for cleanup!)

React Hook Pattern

import { useState, useEffect } from 'react';
import { doc, onSnapshot } from 'firebase/firestore';
import { db } from './firebase';

function useDocument(collectionName, docId) {
  const [data, setData] = useState(null);
  const [loading, setLoading] = useState(true);

  useEffect(() => {
    const unsubscribe = onSnapshot(doc(db, collectionName, docId), (doc) => {
      setData(doc.exists() ? { id: doc.id, ...doc.data() } : null);
      setLoading(false);
    });
    return unsubscribe; // cleanup on unmount
  }, [collectionName, docId]);

  return { data, loading };
}

Authentication

Email/Password

import { 
  signInWithEmailAndPassword, 
  createUserWithEmailAndPassword, 
  signOut,
  onAuthStateChanged 
} from 'firebase/auth';
import { auth } from './firebase';

// Sign up
const userCredential = await createUserWithEmailAndPassword(auth, email, password);
const user = userCredential.user;

// Sign in
await signInWithEmailAndPassword(auth, email, password);

// Sign out
await signOut(auth);

// Listen to auth state
onAuthStateChanged(auth, (user) => {
  if (user) {
    console.log('Logged in:', user.uid);
  } else {
    console.log('Logged out');
  }
});

Google Sign-In

import { signInWithPopup, GoogleAuthProvider } from 'firebase/auth';
import { auth } from './firebase';

const provider = new GoogleAuthProvider();
const result = await signInWithPopup(auth, provider);
const user = result.user;

Auth Context (React)

import { createContext, useContext, useEffect, useState } from 'react';
import { onAuthStateChanged } from 'firebase/auth';
import { auth } from './firebase';

const AuthContext = createContext({});

export function AuthProvider({ children }) {
  const [user, setUser] = useState(null);
  const [loading, setLoading] = useState(true);

  useEffect(() => {
    const unsubscribe = onAuthStateChanged(auth, (user) => {
      setUser(user);
      setLoading(false);
    });
    return unsubscribe;
  }, []);

  return (
    <AuthContext.Provider value={{ user, loading }}>
      {children}
    </AuthContext.Provider>
  );
}

export const useAuth = () => useContext(AuthContext);

Storage (File Uploads)

import { ref, uploadBytes, getDownloadURL } from 'firebase/storage';
import { storage } from './firebase';

// Upload file
const storageRef = ref(storage, `uploads/${file.name}`);
await uploadBytes(storageRef, file);

// Get download URL
const url = await getDownloadURL(storageRef);
console.log('File URL:', url);

Common Errors & Fixes

Security Rules Quick Reference

Development (allow everything — NOT for production):

rules_version = '2';
service cloud.firestore {
  match /databases/{database}/documents {
    match /{document=**} {
      allow read, write: if true;
    }
  }
}

Allow authenticated users only:

rules_version = '2';
service cloud.firestore {
  match /databases/{database}/documents {
    match /{document=**} {
      allow read, write: if request.auth != null;
    }
  }
}

Users can only access their own data:

rules_version = '2';
service cloud.firestore {
  match /databases/{database}/documents {
    match /users/{userId} {
      allow read, write: if request.auth != null && request.auth.uid == userId;
    }
    match /users/{userId}/posts/{postId} {
      allow read: if true;
      allow write: if request.auth != null && request.auth.uid == userId;
    }
  }
}

Firebase CLI

# Install
npm install -g firebase-tools

# Login
firebase login

# Initialize project
firebase init

# Deploy rules
firebase deploy --only firestore:rules

# Deploy hosting
firebase deploy --only hosting

# View logs
firebase functions:log

Debugging Tips

1. Check the Firebase Console — see actual data and errors
2. Check auth state — console.log(auth.currentUser)
3. Check network tab — see actual requests/responses
4. Rules Playground — test rules in Firebase Console
5. Restart dev server after changing .env.local
6. Check indexes — Firestore → Indexes in console
7. Use emulators — firebase emulators:start for local testing