TypeScript-first philosophy in NestJS - Mini Project: Build & Apply

Building a Simple NestJS Service with TypeScript-First Philosophy

📖 Scenario: You are creating a small backend service using NestJS. NestJS encourages a TypeScript-first approach, meaning you write your data types and logic in TypeScript first, which helps catch errors early and makes your code easier to understand.In this project, you will create a simple service that manages a list of books with their titles and authors.

🎯 Goal: Build a NestJS service that stores a list of books using TypeScript interfaces and classes. You will define the data structure, configure a service variable, implement a method to retrieve books, and complete the service class.

📋 What You'll Learn

Create a TypeScript interface for a Book with title and author as strings

Create a service class called BooksService

Add a private array variable books of type Book[] with initial data

Implement a method getAllBooks() that returns the array of books

Complete the service class with the correct export statement

💡 Why This Matters

🌍 Real World

Backend services often manage data with clear types to avoid bugs. NestJS uses TypeScript-first philosophy to help developers write safer and clearer code.

💼 Career

Understanding how to define data types and services in NestJS is essential for backend development roles using modern TypeScript frameworks.

1

Define the Book interface

Create a TypeScript interface called Book with two string properties: title and author.

NestJS

// Define the Book interface with title and author as strings
// Your code here

Need a hint?

Use the interface keyword to define the shape of a book object.

2

Create the BooksService class with initial data

Create a class called BooksService. Inside it, add a private variable called books of type Book[] and initialize it with two books: { title: 'The Hobbit', author: 'J.R.R. Tolkien' } and { title: '1984', author: 'George Orwell' }.

NestJS

export interface Book {
  title: string;
  author: string;
}

// Create BooksService class with private books array
// Your code here

Need a hint?

Use private books: Book[] = [...] inside the class to store the books.

3

Add a method to get all books

Inside the BooksService class, add a public method called getAllBooks() that returns the books array.

NestJS

export interface Book {
  title: string;
  author: string;
}

export class BooksService {
  private books: Book[] = [
    { title: 'The Hobbit', author: 'J.R.R. Tolkien' },
    { title: '1984', author: 'George Orwell' }
  ];

  // Add getAllBooks method below
  // Your code here
}

Need a hint?

Define a method that returns the private books array.

4

Export the BooksService class

Make sure the BooksService class is exported so it can be used in other parts of the application.

NestJS

export interface Book {
  title: string;
  author: string;
}

// Ensure BooksService class is exported
// Your code here

Need a hint?

Use the export keyword before the class declaration.