Response methods and status codes in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to send a 200 OK status with a JSON message.

Node.js

res.status([1]).json({ message: 'Success' });

Drag options to blanks, or click blank then click option'

A500

B404

C301

D200

Attempts:

3 left

💡 Hint

Common Mistakes

Using 404 or 500 which indicate errors instead of success.

Forgetting to set the status code before sending JSON.

The status(200) sets the HTTP status code to 200, which means OK. Then json() sends the JSON response.

2fill in blank

medium

Complete the code to send a 404 Not Found status with a plain text message.

Node.js

res.status([1]).send('Page not found');

Drag options to blanks, or click blank then click option'

A500

B200

C404

D403

Attempts:

3 left

💡 Hint

Common Mistakes

Using 200 which means success instead of 404.

Using json() instead of send() for plain text.

The status(404) sets the HTTP status code to 404, meaning the requested resource was not found.

3fill in blank

hard

Fix the error in the code to correctly send a 201 Created status with JSON data.

Node.js

res.[1](201).json({ id: 123, message: 'Created' });

Drag options to blanks, or click blank then click option'

Astatus

Bsend

Cjson

Dwrite

Attempts:

3 left

💡 Hint

Common Mistakes

Using send() instead of status() to set status code.

Not chaining json() after status().

The status() method sets the HTTP status code. Then json() sends the JSON response. Using send() or write() alone won't set the status code properly.

4fill in blank

hard

Fill both blanks to send a 500 Internal Server Error with a JSON error message.

Node.js

res.[1]([2]).json({ error: 'Server error' });

Drag options to blanks, or click blank then click option'

Astatus

Bsend

C500

D404

Attempts:

3 left

💡 Hint

Common Mistakes

Using send instead of status to set status code.

Using 404 instead of 500 for server errors.

Use status(500) to set the HTTP status code to Internal Server Error, then send JSON with json().

5fill in blank

hard

Fill all three blanks to send a 302 redirect to '/login' with a plain text message.

Node.js

res.[1]([2]).[3]('Redirecting to login');

Drag options to blanks, or click blank then click option'

Astatus

B302

Csend

Djson

Attempts:

3 left

💡 Hint

Common Mistakes

Using json() instead of send() for plain text.

Using wrong status code like 200 or 404.

Use status(302) to set the redirect status, then send() to send the plain text message.

Practice

1. What does the res.status(404) method do in a Node.js response?

easy

A. Redirects the client to a page named '404'

B. Sends the response body with the text '404'

C. Sets the HTTP status code to 404 (Not Found) for the response

D. Ends the response without sending any data

Solution

1. Step 1: Understand the purpose of res.status()

   This method sets the HTTP status code that tells the browser what happened with the request.

2. Step 2: Identify the meaning of 404 status code

   Status code 404 means 'Not Found', indicating the requested resource does not exist.

3. Final Answer:

   Sets the HTTP status code to 404 (Not Found) for the response -> Option C

4. Quick Check:

   Status code 404 = Not Found [OK]

Hint: Status codes tell browser what happened; 404 means not found [OK]

Common Mistakes:

• Thinking res.status sends the response body
• Confusing status code with redirect
• Assuming res.status ends the response

2. Which of the following is the correct way to send a JSON response with status 200 in Express?

easy

A. res.status(200).json({ message: 'OK' })

B. res.send(200).json({ message: 'OK' })

C. res.json(200, { message: 'OK' })

D. res.status(200).sendJson({ message: 'OK' })

Solution

1. Step 1: Recall Express response chaining

   Use res.status(code) to set status, then call json() to send JSON data.

2. Step 2: Check each option's syntax

   res.status(200).json({ message: 'OK' }) correctly chains status(200) and json(). Others misuse method order or names.

3. Final Answer:

   res.status(200).json({ message: 'OK' }) -> Option A

4. Quick Check:

   Set status then send JSON = res.status(200).json({ message: 'OK' }) [OK]

Hint: Set status first, then call json() to send data [OK]

Common Mistakes:

• Calling send before status
• Using non-existent sendJson method
• Passing status code inside json()

3. What will the following Express code send to the client?

app.get('/test', (req, res) => {
  res.status(201).send('Created');
});

medium

A. A response with status 200 and body 'Created'

B. A response with status 201 and body 'Created'

C. A response with status 201 and no body

D. An error because send() cannot follow status()

Solution

1. Step 1: Understand status and send chaining

   res.status(201) sets status code 201 (Created), then send('Created') sends that text as the response body.

2. Step 2: Confirm behavior of Express response

   Express allows chaining status and send; the response will have status 201 and body 'Created'.

3. Final Answer:

   A response with status 201 and body 'Created' -> Option B

4. Quick Check:

   Status 201 + send text = A response with status 201 and body 'Created' [OK]

Hint: status sets code, send sends body; chaining works [OK]

Common Mistakes:

• Assuming default status 200 is sent
• Thinking send() clears status
• Believing chaining status and send causes error

4. Identify the error in this Express code snippet:

app.get('/redirect', (req, res) => {
  res.send('Redirecting...');
  res.redirect('/new-url');
});

medium

A. Calling res.redirect after res.send causes an error

B. res.redirect should be called before res.send

C. res.send cannot send strings, only JSON

D. No error; this code works fine

Solution

1. Step 1: Understand response flow in Express

   Once res.send() is called, the response is sent and closed.

2. Step 2: Check order of methods

   Calling res.redirect() after res.send() tries to send headers again, causing an error.

3. Final Answer:

   Calling res.redirect after res.send causes an error -> Option A

4. Quick Check:

   Send ends response; redirect after send fails [OK]

Hint: Send or redirect ends response; don't call both [OK]

Common Mistakes:

• Thinking order doesn't matter
• Believing send only works with JSON
• Assuming no error on multiple sends

5. You want to send a JSON response with status 400 and a message 'Invalid input'. Which code correctly does this in Express?

hard

A. res.json(400, { error: 'Invalid input' })

B. res.sendStatus(400).json({ error: 'Invalid input' })

C. res.status(400).send('Invalid input')

D. res.status(400).json({ error: 'Invalid input' })

Solution

1. Step 1: Set the status code correctly

   Use res.status(400) to set the HTTP status to 400 (Bad Request).

2. Step 2: Send JSON response

   Use json() to send the JSON object with the error message.

3. Step 3: Check incorrect options

   res.json(400, { error: 'Invalid input' }) uses wrong method signature (sends 400 as JSON body with status 200); res.status(400).send('Invalid input') sends plain text string (Content-Type text/html) instead of JSON; res.sendStatus(400).json({ error: 'Invalid input' }) ends response with sendStatus before json.

4. Final Answer:

   res.status(400).json({ error: 'Invalid input' }) -> Option D

5. Quick Check:

   Status then json() sends JSON with code [OK]

Hint: Use status() then json() to send JSON with status [OK]

Common Mistakes:

• Passing status code inside json()
• Using send instead of json for JSON data
• Calling sendStatus before json