HTTP methods and CRUD mapping in Node.js - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Mapping HTTP methods to CRUD operations

Which HTTP method is correctly paired with the Update operation in CRUD?

A PUT

B POST

C GET

D DELETE

💡 Hint

Think about which method replaces or modifies existing data.

PUT is used to update or replace existing resources, matching the Update operation in CRUD.

❓ component_behavior

intermediate

Behavior of HTTP DELETE method

What is the expected behavior when a server receives an HTTP DELETE request for a resource?

A The server creates a new resource.

B The server removes the specified resource.

C The server retrieves the resource data.

D The server updates the resource partially.

💡 Hint

DELETE is about removing something.

DELETE requests instruct the server to remove the specified resource.

📝 Syntax

advanced

Correct HTTP method for partial update

Which HTTP method is designed for partial updates of a resource?

A PATCH

B PUT

C POST

D GET

💡 Hint

It modifies only parts of a resource, not the whole.

PATCH is used for partial updates, unlike PUT which replaces the entire resource.

❓ state_output

advanced

Result of GET request on a resource

What is the typical result of a successful HTTP GET request to a resource endpoint?

A A new resource is created and its ID is returned.

B The resource is updated with new data.

C The resource data is returned without modifying it.

D The resource is deleted and a confirmation is returned.

💡 Hint

GET is used to read data, not change it.

GET requests retrieve resource data without changing the server state.

🔧 Debug

expert

Identify the incorrect HTTP method for Create operation

Which HTTP method is incorrectly used for creating a new resource?

Node.js

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

app.post('/items', (req, res) => {
  // Create new item logic
  res.status(201).send('Created');
});

app.get('/items', (req, res) => {
  // List items logic
  res.send('List');
});

app.put('/items', (req, res) => {
  // Intended to create new item but used PUT
  res.status(201).send('Created with PUT');
});

A GET is used to create a new resource, which is incorrect.

B POST is the correct method to create a new resource.

C PUT can be used to create a resource but only at a specific URL.

D PUT used without specifying resource ID is incorrect for creation.

💡 Hint

PUT on a collection endpoint like /items is incorrect for creation.

PUT is typically used for full replacement or conditional creation at a specific resource URL (e.g., /items/123). Using PUT on a collection endpoint like /items for creation is non-standard; POST is the standard method.

Practice

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

easy

A. GET

B. POST

C. PUT

D. DELETE

Solution

1. Step 1: Understand HTTP methods and their purposes

   In RESTful APIs, GET is used to read or retrieve data from the server.

2. Step 2: Match the method to the action

   POST creates, PUT updates, and DELETE removes data, so only GET fits retrieving data.

3. Final Answer:

   GET -> Option A

4. Quick Check:

   Read = GET [OK]

Hint: GET is for reading data, like looking at a book [OK]

Common Mistakes:

• Confusing POST with GET
• Using DELETE to fetch data
• Thinking PUT retrieves data

2. Which of the following Express route definitions correctly handles updating a resource using the HTTP method for update?

easy

A. app.get('/item/:id', handler)

B. app.post('/item/:id', handler)

C. app.put('/item/:id', handler)

D. app.delete('/item/:id', handler)

Solution

1. Step 1: Identify the HTTP method for updating

   Updating a resource uses the PUT method in RESTful APIs.

2. Step 2: Match Express method to HTTP method

   Express uses app.put() to handle PUT requests, so app.put('/item/:id', handler) is correct.

3. Final Answer:

   app.put('/item/:id', handler) -> Option C

4. Quick Check:

   Update = PUT = app.put() [OK]

Hint: Use app.put() for updates in Express routes [OK]

Common Mistakes:

• Using app.post() for updates
• Using app.get() for updates
• Confusing app.delete() with update

3. Consider this Express code snippet:

app.delete('/user/:id', (req, res) => {
  res.send(`Deleted user ${req.params.id}`);
});

// Client sends DELETE request to /user/42

What will the server respond with?

medium

A. "Updated user 42"

B. "Deleted user 42"

C. "Created user 42"

D. 404 Not Found

Solution

1. Step 1: Understand the route and HTTP method

   The route listens for DELETE requests on /user/:id. The client sends a DELETE request to /user/42.

2. Step 2: Analyze the response sent

   The handler sends back the string Deleted user 42 using the id from the URL.

3. Final Answer:

   "Deleted user 42" -> Option B

4. Quick Check:

   DELETE request responds with deletion message [OK]

Hint: DELETE routes respond with deletion confirmation [OK]

Common Mistakes:

• Confusing DELETE with POST response
• Expecting 404 instead of success message
• Mixing up URL parameters

4. What is wrong with this Express route for creating a new item?

app.get('/items', (req, res) => {
  // code to add new item
  res.send('Item created');
});

medium

A. Missing route parameter for item ID

B. Route path should be '/item' not '/items'

C. Response message is incorrect

D. GET method should not be used to create data

Solution

1. Step 1: Identify the HTTP method used

   The route uses GET, which is meant for reading data, not creating.

2. Step 2: Match method to CRUD action

   Creating new data should use POST, so using GET here is incorrect.

3. Final Answer:

   GET method should not be used to create data -> Option D

4. Quick Check:

   Create = POST, not GET [OK]

Hint: Use POST to create, not GET [OK]

Common Mistakes:

• Using GET to create resources
• Ignoring HTTP method semantics
• Assuming route path is the issue

5. You want to build an Express API that allows clients to create, read, update, and delete "products". Which set of route definitions correctly maps HTTP methods to CRUD actions?

hard

A. app.post('/products', createHandler); app.get('/products/:id', readHandler); app.put('/products/:id', updateHandler); app.delete('/products/:id', deleteHandler);

B. app.get('/products', createHandler); app.post('/products/:id', readHandler); app.put('/products', updateHandler); app.delete('/products', deleteHandler);

C. app.put('/products', createHandler); app.get('/products/:id', readHandler); app.post('/products/:id', updateHandler); app.delete('/products/:id', deleteHandler);

D. app.delete('/products', createHandler); app.put('/products/:id', readHandler); app.post('/products/:id', updateHandler); app.get('/products/:id', deleteHandler);

Solution

1. Step 1: Match each CRUD action to correct HTTP method

   Create = POST, Read = GET, Update = PUT, Delete = DELETE.

2. Step 2: Check route paths and handlers

   app.post('/products', createHandler); app.get('/products/:id', readHandler); app.put('/products/:id', updateHandler); app.delete('/products/:id', deleteHandler); uses POST /products for create, GET /products/:id for read, PUT /products/:id for update, and DELETE /products/:id for delete, which is correct.

3. Final Answer:

   app.post('/products', createHandler); app.get('/products/:id', readHandler); app.put('/products/:id', updateHandler); app.delete('/products/:id', deleteHandler); -> Option A

4. Quick Check:

   POST=create, GET=read, PUT=update, DELETE=delete [OK]

Hint: Remember CRUD: POST, GET, PUT, DELETE order [OK]

Common Mistakes:

• Mixing POST and GET methods
• Using wrong paths for actions
• Assigning update to POST instead of PUT