How to Order Firestore Documents by Timestamp

1import {
2  getFirestore, collection, addDoc, updateDoc, doc,
3  serverTimestamp
4} from 'firebase/firestore';
5
6const db = getFirestore();
7
8// Create a document with a server timestamp
9async function createPost(title: string, content: string) {
10  const docRef = await addDoc(collection(db, 'posts'), {
11    title,
12    content,
13    createdAt: serverTimestamp(),
14    updatedAt: serverTimestamp()
15  });
16  return docRef;
17}
18
19// Update a document and refresh the updatedAt timestamp
20async function updatePost(postId: string, content: string) {
21  const postRef = doc(db, 'posts', postId);
22  await updateDoc(postRef, {
23    content,
24    updatedAt: serverTimestamp()
25  });
26}

1import {
2  getFirestore, collection, query, orderBy, limit, getDocs
3} from 'firebase/firestore';
4
5const db = getFirestore();
6
7// Get the 20 most recent posts (newest first)
8async function getRecentPosts() {
9  const q = query(
10    collection(db, 'posts'),
11    orderBy('createdAt', 'desc'),
12    limit(20)
13  );
14  const snapshot = await getDocs(q);
15  return snapshot.docs.map(doc => ({
16    id: doc.id,
17    ...doc.data()
18  }));
19}
20
21// Get the oldest posts first
22async function getOldestPosts() {
23  const q = query(
24    collection(db, 'posts'),
25    orderBy('createdAt', 'asc'),
26    limit(20)
27  );
28  const snapshot = await getDocs(q);
29  return snapshot.docs.map(doc => ({
30    id: doc.id,
31    ...doc.data()
32  }));
33}

1import {
2  getFirestore, collection, query, where, orderBy, limit, getDocs
3} from 'firebase/firestore';
4
5const db = getFirestore();
6
7// Get recent posts by a specific author (requires composite index)
8async function getPostsByAuthor(authorId: string) {
9  const q = query(
10    collection(db, 'posts'),
11    where('authorId', '==', authorId),
12    orderBy('createdAt', 'desc'),
13    limit(20)
14  );
15  const snapshot = await getDocs(q);
16  return snapshot.docs.map(doc => ({
17    id: doc.id,
18    ...doc.data()
19  }));
20}
21
22// Get posts from the last 7 days
23async function getRecentWeekPosts() {
24  const oneWeekAgo = new Date();
25  oneWeekAgo.setDate(oneWeekAgo.getDate() - 7);
26
27  const q = query(
28    collection(db, 'posts'),
29    where('createdAt', '>=', oneWeekAgo),
30    orderBy('createdAt', 'desc')
31  );
32  const snapshot = await getDocs(q);
33  return snapshot.docs.map(doc => ({
34    id: doc.id,
35    ...doc.data()
36  }));
37}

1import {
2  getFirestore, collection, query, orderBy, limit,
3  startAfter, getDocs, QueryDocumentSnapshot
4} from 'firebase/firestore';
5
6const db = getFirestore();
7const PAGE_SIZE = 20;
8
9// First page
10async function getFirstPage() {
11  const q = query(
12    collection(db, 'posts'),
13    orderBy('createdAt', 'desc'),
14    limit(PAGE_SIZE)
15  );
16  const snapshot = await getDocs(q);
17  const lastDoc = snapshot.docs[snapshot.docs.length - 1];
18  return {
19    posts: snapshot.docs.map(doc => ({ id: doc.id, ...doc.data() })),
20    lastDoc
21  };
22}
23
24// Next page using cursor
25async function getNextPage(lastDoc: QueryDocumentSnapshot) {
26  const q = query(
27    collection(db, 'posts'),
28    orderBy('createdAt', 'desc'),
29    startAfter(lastDoc),
30    limit(PAGE_SIZE)
31  );
32  const snapshot = await getDocs(q);
33  const newLastDoc = snapshot.docs[snapshot.docs.length - 1];
34  return {
35    posts: snapshot.docs.map(doc => ({ id: doc.id, ...doc.data() })),
36    lastDoc: newLastDoc
37  };
38}

1import {
2  getFirestore, collection, query, orderBy, limit,
3  onSnapshot
4} from 'firebase/firestore';
5
6const db = getFirestore();
7
8function subscribeToRecentPosts(
9  callback: (posts: any[]) => void
10) {
11  const q = query(
12    collection(db, 'posts'),
13    orderBy('createdAt', 'desc'),
14    limit(50)
15  );
16
17  const unsubscribe = onSnapshot(q, (snapshot) => {
18    const posts = snapshot.docs.map(doc => ({
19      id: doc.id,
20      ...doc.data()
21    }));
22    callback(posts);
23  }, (error) => {
24    console.error('Snapshot listener error:', error);
25  });
26
27  return unsubscribe;
28}