Route handlers (GET, POST, PUT, DELETE) in NestJS - Mini Project: Build & Apply

Basic CRUD API with NestJS Route Handlers

📖 Scenario: You are building a simple API for managing a list of books in a library. Each book has a title and an author.This API will let users get the list of books, add a new book, update an existing book, and delete a book.

🎯 Goal: Create a NestJS controller with route handlers for GET, POST, PUT, and DELETE to manage books.

📋 What You'll Learn

Create a controller class named BooksController.

Create a property books initialized with an array of two book objects: { id: 1, title: '1984', author: 'George Orwell' } and { id: 2, title: 'The Hobbit', author: 'J.R.R. Tolkien' }.

Add a GET route handler method getAllBooks() that returns the books array.

Add a POST route handler method addBook() that accepts a book object and adds it to books.

Add a PUT route handler method updateBook() that accepts an id parameter and a book object, then updates the matching book in books.

Add a DELETE route handler method deleteBook() that accepts an id parameter and removes the matching book from books.

💡 Why This Matters

🌍 Real World

APIs like this are common in web applications to manage data resources such as books, users, or products.

💼 Career

Understanding how to create route handlers for different HTTP methods is essential for backend development roles using NestJS or similar frameworks.

1

Create the initial books data array

Create a controller class named BooksController with a property books initialized to an array containing exactly these two objects: { id: 1, title: '1984', author: 'George Orwell' } and { id: 2, title: 'The Hobbit', author: 'J.R.R. Tolkien' }.

NestJS

export class BooksController {
  // Your code here
}

Need a hint?

Define a class named BooksController. Inside it, create a property books and assign the array with the two book objects.

2

Add a GET route handler to return all books

Add a method named getAllBooks() decorated with @Get() that returns the books array.

NestJS

export class BooksController {
  books = [
    { id: 1, title: '1984', author: 'George Orwell' },
    { id: 2, title: 'The Hobbit', author: 'J.R.R. Tolkien' }
  ];

  // Add a GET route handler method getAllBooks() below
}

Need a hint?

Use the @Get() decorator above the getAllBooks() method. Return the books property inside the method.

3

Add POST and PUT route handlers to add and update books

Add a POST route handler method addBook() decorated with @Post() that accepts a book object parameter decorated with @Body() and adds it to books. Also add a PUT route handler method updateBook() decorated with @Put(':id') that accepts an id parameter decorated with @Param('id') and a book object decorated with @Body(), then updates the matching book in books.

NestJS

import { Controller, Get, Post, Put, Body, Param } from '@nestjs/common';

@Controller('books')
export class BooksController {
  books = [
    { id: 1, title: '1984', author: 'George Orwell' },
    { id: 2, title: 'The Hobbit', author: 'J.R.R. Tolkien' }
  ];

  @Get()
  getAllBooks() {
    return this.books;
  }

  // Add POST and PUT route handlers addBook() and updateBook() below
}

Need a hint?

Use @Post() and @Put(':id') decorators. Use @Body() to get the book data and @Param('id') to get the id. Update the books array accordingly.

4

Add DELETE route handler to remove a book

Add a DELETE route handler method deleteBook() decorated with @Delete(':id') that accepts an id parameter decorated with @Param('id') and removes the matching book from books.

NestJS

import { Controller, Get, Post, Put, Delete, Body, Param } from '@nestjs/common';

@Controller('books')
export class BooksController {
  books = [
    { id: 1, title: '1984', author: 'George Orwell' },
    { id: 2, title: 'The Hobbit', author: 'J.R.R. Tolkien' }
  ];

  @Get()
  getAllBooks() {
    return this.books;
  }

  @Post()
  addBook(@Body() book: { id: number; title: string; author: string }) {
    this.books.push(book);
  }

  @Put(':id')
  updateBook(
    @Param('id') id: string,
    @Body() updatedBook: { title: string; author: string }
  ) {
    const bookId = Number(id);
    const bookIndex = this.books.findIndex(book => book.id === bookId);
    if (bookIndex !== -1) {
      this.books[bookIndex] = { id: bookId, ...updatedBook };
    }
  }

  // Add DELETE route handler deleteBook() below
}

Need a hint?

Use the @Delete(':id') decorator. Use @Param('id') to get the id. Use filter to remove the book from the array.