HTTP methods for CRUD operations in Express - Mini Project: Build & Apply

HTTP methods for CRUD operations

📖 Scenario: You are building a simple Express server to manage a list of books. Each book has an id and a title. You want to allow users to create, read, update, and delete books using HTTP methods.

🎯 Goal: Create an Express app that supports CRUD operations on a books array using the correct HTTP methods: GET, POST, PUT, and DELETE.

📋 What You'll Learn

Create an array called books with two book objects having id and title.

Add a variable called nextId to track the next book ID.

Create a GET route at /books to return all books.

Create a POST route at /books to add a new book with a unique id.

Create a PUT route at /books/:id to update the title of a book by id.

Create a DELETE route at /books/:id to remove a book by id.

💡 Why This Matters

🌍 Real World

Web servers often use HTTP methods to manage data resources like users, products, or posts. This project shows how to build a simple API for managing books.

💼 Career

Understanding HTTP methods and Express routing is essential for backend web development jobs, API design, and full-stack roles.

1

Create the initial books array

Create an array called books with two objects: { id: 1, title: '1984' } and { id: 2, title: 'Brave New World' }.

Express

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

Hint

Use const books = [ ... ] with two objects inside.

2

Add a nextId variable

Add a variable called nextId and set it to 3 to track the next book ID.

Express

const books = [
  { id: 1, title: '1984' },
  { id: 2, title: 'Brave New World' }
];

// Add nextId variable here
// Your code here

Hint

Use let nextId = 3; to allow incrementing later.

3

Create GET and POST routes

Create a GET route at /books that sends the books array as JSON. Then create a POST route at /books that adds a new book with a unique id from nextId and increments nextId. Use req.body.title for the new book's title.

Express

const books = [
  { id: 1, title: '1984' },
  { id: 2, title: 'Brave New World' }
];

let nextId = 3;

// Create GET /books route
// Create POST /books route
// Your code here

Hint

Use app.get('/books', (req, res) => { res.json(books); }) and app.post('/books', (req, res) => { ... }).

4

Create PUT and DELETE routes

Create a PUT route at /books/:id that updates the title of the book with the matching id from req.params.id. Then create a DELETE route at /books/:id that removes the book with the matching id. Use res.status(204).end() after deletion.

Express

const books = [
  { id: 1, title: '1984' },
  { id: 2, title: 'Brave New World' }
];

let nextId = 3;

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

app.post('/books', (req, res) => {
  const newBook = { id: nextId++, title: req.body.title };
  books.push(newBook);
  res.status(201).json(newBook);
});

// Create PUT /books/:id route
// Create DELETE /books/:id route
// Your code here

Hint

Use app.put('/books/:id', ...) to find and update the book, and app.delete('/books/:id', ...) to remove it.

Practice

1. Which HTTP method is typically used in Express to retrieve data from a server?

easy

A. PUT

B. POST

C. DELETE

D. GET

Solution

1. Step 1: Understand HTTP methods purpose

   GET is used to read or retrieve data from the server without changing it.

2. Step 2: Match method to action

   Since the question asks for retrieving data, GET is the correct method.

3. Final Answer:

   GET -> Option D

4. Quick Check:

   Retrieve data = GET [OK]

Hint: GET always reads data without changing it [OK]

Common Mistakes:

• Confusing POST with GET for reading data
• Using DELETE to get data
• Thinking PUT retrieves data

2. Which of the following is the correct Express syntax to handle a POST request to the path /users?

easy

A. app.get('/users', (req, res) => { ... })

B. app.put('/users', (req, res) => { ... })

C. app.post('/users', (req, res) => { ... })

D. app.delete('/users', (req, res) => { ... })

Solution

1. Step 1: Identify method for creating data

   POST is used to create new data on the server.

2. Step 2: Match Express syntax to POST

   app.post('/users', ...) correctly handles POST requests to /users.

3. Final Answer:

   app.post('/users', (req, res) => { ... }) -> Option C

4. Quick Check:

   POST creates data = app.post() [OK]

Hint: Use app.post() for creating new data routes [OK]

Common Mistakes:

• Using app.get() for POST requests
• Confusing app.put() with app.post()
• Writing app.delete() for creation

3. What will be the response status code if you define this Express route and send a request to PUT /items/5?

app.put('/items/:id', (req, res) => {
  res.status(200).send(`Updated item ${req.params.id}`);
});

medium

A. 200 OK

B. 201 Created

C. 500 Internal Server Error

D. 404 Not Found

Solution

1. Step 1: Analyze route and method

   The route handles PUT requests to /items/:id, so /items/5 matches with id=5.

2. Step 2: Check response status code

   The code explicitly sets status 200 and sends a message, so response status is 200 OK.

3. Final Answer:

   200 OK -> Option A

4. Quick Check:

   PUT route sends status 200 = 200 OK [OK]

Hint: Check res.status() for response code [OK]

Common Mistakes:

• Assuming 201 Created for PUT
• Thinking 404 if route exists
• Confusing 500 error without code

4. Identify the error in this Express route meant to delete a user by ID:

app.delete('/users/:id', (req, res) => {
  const userId = req.params;
  deleteUser(userId);
  res.send('User deleted');
});

medium

A. req.params should be req.params.id to get the ID

B. deleteUser is not a valid Express method

C. res.send should be res.status(204).send()

D. Route path should be '/user/:id' not '/users/:id'

Solution

1. Step 1: Check how userId is assigned

   req.params is an object; to get the ID string, use req.params.id.

2. Step 2: Understand deleteUser usage

   deleteUser likely expects an ID string, so passing the whole params object is wrong.

3. Final Answer:

   req.params should be req.params.id to get the ID -> Option A

4. Quick Check:

   Use req.params.id for ID value [OK]

Hint: Use req.params.id to access route parameters [OK]

Common Mistakes:

• Passing whole req.params object instead of ID
• Confusing route path naming
• Assuming deleteUser is Express built-in

5. You want to update a user's email fully using Express. Which HTTP method and route setup is best practice for this operation?

hard

A. app.post('/users/:id', (req, res) => { ... })

B. app.put('/users/:id', (req, res) => { ... })

C. app.get('/users/:id', (req, res) => { ... })

D. app.delete('/users/:id', (req, res) => { ... })

Solution

1. Step 1: Identify method for full update

   PUT is the HTTP method used to fully update existing data.

2. Step 2: Match route to user ID

   Route '/users/:id' targets a specific user by ID for update.

3. Final Answer:

   app.put('/users/:id', (req, res) => { ... }) -> Option B

4. Quick Check:

   Full update = PUT method [OK]

Hint: Use PUT with ID route for full updates [OK]

Common Mistakes:

• Using POST for updates instead of creation
• Using GET or DELETE for updating data
• Not including :id in route for specific user