HTTP methods for CRUD operations in Express - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

Identify the HTTP method for creating a new resource

In an Express app, which HTTP method is typically used to create a new resource on the server?

A GET

B POST

C DELETE

D PUT

💡 Hint

Think about which method sends data to the server to add something new.

The POST method is used to send data to the server to create a new resource. GET is for fetching data, PUT is for updating, and DELETE is for removing.

❓ component_behavior

intermediate

Choose the HTTP method for updating an existing resource

Which HTTP method should you use in Express to update an existing resource completely?

A GET

B POST

C PATCH

D PUT

💡 Hint

This method replaces the entire resource with new data.

PUT replaces the entire resource with the data sent. PATCH is for partial updates, POST is for creating, and GET is for reading.

📝 Syntax

advanced

Identify the correct Express route for deleting a resource

Which Express route correctly handles deleting a resource by its ID?

A app.delete('/items/:id', (req, res) => { /* delete logic */ })

B app.get('/items/:id', (req, res) => { /* delete logic */ })

C app.post('/items/:id', (req, res) => { /* delete logic */ })

D app.put('/items/:id', (req, res) => { /* delete logic */ })

💡 Hint

Deleting a resource uses a specific HTTP method matching the route.

app.delete defines a route that listens for DELETE requests, which is the correct method for deleting resources. Other methods are for different actions.

❓ state_output

advanced

What is the response status code after a successful resource update?

In Express, after successfully updating a resource with PUT, which HTTP status code is most appropriate to send back?

A 200 OK

B 201 Created

C 204 No Content

D 404 Not Found

💡 Hint

The resource exists and was updated successfully.

200 OK means the update was successful and the server is returning the updated resource or confirmation. 201 is for creation, 204 means success with no content, and 404 means resource not found.

🧠 Conceptual

expert

Understanding idempotency in HTTP methods for CRUD

Which HTTP method used in CRUD operations is idempotent, meaning multiple identical requests have the same effect as one request?

A POST

B PUT

C PATCH

D DELETE

💡 Hint

Idempotent methods do not change the result if repeated multiple times.

PUT is idempotent because updating a resource with the same data multiple times results in the same state. POST is not idempotent because it creates new resources each time. PATCH may not be idempotent depending on the patch. DELETE is idempotent because deleting the same resource multiple times has the same effect as deleting once.

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