Cursor-based pagination (startAfter, endBefore) in Firebase - Mini Project: Build & Apply

Cursor-based pagination (startAfter, endBefore)

📖 Scenario: You are building a simple app that shows a list of books stored in a Firebase Firestore database. The list can be very long, so you want to show only a few books at a time and let users move forward or backward through the list.

🎯 Goal: Create a Firestore query that fetches books in pages of 3 items using cursor-based pagination with startAfter and endBefore methods.

📋 What You'll Learn

Create a Firestore collection reference called booksRef pointing to the 'books' collection.

Create a query to fetch the first 3 books ordered by the field title.

Add a variable lastVisible to store the last document snapshot from the current page.

Create a query to fetch the next 3 books using startAfter(lastVisible).

Create a query to fetch the previous 3 books using endBefore(firstVisible).

💡 Why This Matters

🌍 Real World

Cursor-based pagination is used in apps to efficiently load large lists of data without overwhelming the user or the database.

💼 Career

Understanding Firestore pagination is important for building scalable cloud applications that handle data smoothly.

1

Set up Firestore collection reference

Create a Firestore collection reference called booksRef that points to the 'books' collection.

Firebase

# Your code here

Need a hint?

Use firestore.collection('books') to get the collection reference.

2

Create initial query for first page

Create a query called firstPageQuery that fetches the first 3 books ordered by the title field.

Firebase

const booksRef = firestore.collection('books');
# Your code here

Need a hint?

Use orderBy('title') and limit(3) on booksRef.

3

Add variable to store last visible document

Create a variable called lastVisible to store the last document snapshot from the current page.

Firebase

const booksRef = firestore.collection('books');
const firstPageQuery = booksRef.orderBy('title').limit(3);
# Your code here

Need a hint?

Initialize lastVisible with null before fetching data.

4

Create queries for next and previous pages

Create two queries: nextPageQuery that fetches the next 3 books using startAfter(lastVisible), and prevPageQuery that fetches the previous 3 books using endBefore(firstVisible). Assume firstVisible is the first document snapshot of the current page.

Firebase

const booksRef = firestore.collection('books');
const firstPageQuery = booksRef.orderBy('title').limit(3);
let lastVisible = null;
# Your code here

Need a hint?

Use startAfter(lastVisible) for next page and endBefore(firstVisible) for previous page queries.