Examples

// ===== 1) Auth + Firestore CRUD (web SDK v10) =====
import { initializeApp } from 'firebase/app';
import { getAuth, onAuthStateChanged, signInWithEmailAndPassword } from 'firebase/auth';
import {
  getFirestore, collection, doc, addDoc, updateDoc, deleteDoc,
  query, where, orderBy, limit, onSnapshot, serverTimestamp,
} from 'firebase/firestore';

const app  = initializeApp({/* config */});
const auth = getAuth(app);
const db   = getFirestore(app);

await signInWithEmailAndPassword(auth, 'alice@example.com', 'hunter2');

const tasks = collection(db, 'tasks');

// Create
const ref = await addDoc(tasks, {
  uid: auth.currentUser!.uid,
  title: 'Buy milk',
  done:  false,
  created_at: serverTimestamp(),
});

// Update
await updateDoc(doc(db, 'tasks', ref.id), { done: true });

// Delete
await deleteDoc(doc(db, 'tasks', ref.id));

// Real-time list of my open tasks
const q = query(tasks,
  where('uid', '==', auth.currentUser!.uid),
  where('done', '==', false),
  orderBy('created_at', 'desc'),
  limit(20));
onSnapshot(q, (snap) => snap.forEach((d) => console.log(d.id, d.data())));

// ===== 2) Firestore security rules — only the owner can read/write =====
// rules.firestore
// rules_version = '2';
// service cloud.firestore {
//   match /databases/{database}/documents {
//     match /tasks/{id} {
//       allow read, update, delete: if request.auth != null
//                                   && resource.data.uid == request.auth.uid;
//       allow create:               if request.auth != null
//                                   && request.resource.data.uid == request.auth.uid;
//     }
//   }
// }

// ===== 3) Cloud Storage upload + signed download URL =====
import { getStorage, ref as sref, uploadBytes, getDownloadURL } from 'firebase/storage';
const storage = getStorage(app);
const file = (document.getElementById('file') as HTMLInputElement).files![0];
const path = \`users/${auth.currentUser!.uid}/receipts/${Date.now()}-${file.name}\`;
await uploadBytes(sref(storage, path), file, { contentType: file.type });
const url = await getDownloadURL(sref(storage, path));
console.log('uploaded to', url);

// ===== 4) Cloud Function (v2) triggered when a task completes =====
// functions/src/index.ts
// import { onDocumentUpdated } from 'firebase-functions/v2/firestore';
// import { logger } from 'firebase-functions';
// export const onTaskDone = onDocumentUpdated('tasks/{id}', async (event) => {
//   const before = event.data?.before.data();
//   const after  = event.data?.after.data();
//   if (!before?.done && after?.done) {
//     logger.info({ id: event.params.id }, 'task completed');
//     // send a push, write an audit row, etc.
//   }
// });

// ===== 5) Firebase Hosting — SPA + serverless backend =====
// firebase.json
// {
//   "hosting": {
//     "public": "dist",
//     "ignore": ["firebase.json", "**/.*", "**/node_modules/**"],
//     "rewrites": [
//       { "source": "/api/**", "function": "api" },
//       { "source": "**",     "destination": "/index.html" }
//     ],
//     "headers": [
//       { "source": "**/*.@(js|css|woff2)",
//         "headers": [{ "key": "Cache-Control", "value": "public, max-age=31536000, immutable" }] }
//     ]
//   }
// }
// firebase deploy --only hosting,functions

// Combine: Auth + Firestore + Hosting = a full-stack app in a weekend.