Repository pattern for data access in Express - Mini Project: Build & Apply

Repository pattern for data access in Express

📖 Scenario: You are building a simple Express app that manages a list of books. To keep your code clean and organized, you will use the repository pattern to handle data access. This means you will create a separate module that manages the books data, so your main app code stays simple and easy to maintain.

🎯 Goal: Build a repository module that stores books data and provides methods to get all books and add a new book. Then use this repository in an Express route to show all books.

📋 What You'll Learn

Create a books array with initial book objects

Create a BookRepository object with methods to get all books and add a book

Use the repository methods inside an Express route to send the list of books as JSON

Set up a basic Express server listening on port 3000

💡 Why This Matters

🌍 Real World

The repository pattern helps keep your Express app organized by separating data access from route handling. This makes your code easier to maintain and test.

💼 Career

Many backend jobs require clean code organization. Using repository pattern is a common practice to manage data access in Node.js and Express applications.

1

DATA SETUP: Create the initial books data array

Create a variable called books that is an array containing these two book objects exactly: { id: 1, title: 'The Hobbit' } and { id: 2, title: '1984' }.

Express

// Create the books array with two book objects
// Your code here

Need a hint?

Use const books = [ ... ] and include the two objects inside the array.

2

CONFIGURATION: Create the BookRepository object

Create a constant called BookRepository that is an object with two methods: getAll which returns the books array, and add which takes a book parameter and pushes it into the books array.

Express

const books = [
  { id: 1, title: 'The Hobbit' },
  { id: 2, title: '1984' }
];

// Create BookRepository object with getAll and add methods
// Your code here

Need a hint?

Define BookRepository as an object with two functions: getAll and add.

3

CORE LOGIC: Use the repository in an Express route

Create an Express app by requiring express and calling express(). Then add a GET route on '/books' that uses BookRepository.getAll() to get all books and sends them as JSON with res.json().

Express

const books = [
  { id: 1, title: 'The Hobbit' },
  { id: 2, title: '1984' }
];

const BookRepository = {
  getAll() {
    return books;
  },
  add(book) {
    books.push(book);
  }
};

// Create Express app and add GET /books route
// Your code here

Need a hint?

Use require('express') and express() to create the app. Then add a GET route on /books that sends JSON from the repository.

4

COMPLETION: Start the Express server on port 3000

Add a line to start the Express app listening on port 3000 using app.listen(3000).

Express

const books = [
  { id: 1, title: 'The Hobbit' },
  { id: 2, title: '1984' }
];

const BookRepository = {
  getAll() {
    return books;
  },
  add(book) {
    books.push(book);
  }
};

const express = require('express');
const app = express();

app.get('/books', (req, res) => {
  const allBooks = BookRepository.getAll();
  res.json(allBooks);
});

// Start server on port 3000
// Your code here

Need a hint?

Use app.listen(3000) to start the server on port 3000.