Status code conventions in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to send a 200 OK status response in Express.

Express

app.get('/home', (req, res) => {
  res.status([1]).send('Welcome!');
});

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

A200

B404

C500

D301

Attempts:

3 left

💡 Hint

Common Mistakes

Using 404 or 500 which mean errors, not success.

The status code 200 means the request was successful and the server is sending the requested data.

2fill in blank

medium

Complete the code to send a 404 Not Found status when a resource is missing.

Express

app.get('/item/:id', (req, res) => {
  const item = findItem(req.params.id);
  if (!item) {
    res.status([1]).send('Item not found');
  }
});

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

A500

B403

C200

D404

Attempts:

3 left

💡 Hint

Common Mistakes

Using 200 which means success, or 500 which means server error.

404 means the requested resource was not found on the server.

3fill in blank

hard

Fix the error in the code to send a 201 Created status after a new user is added.

Express

app.post('/users', (req, res) => {
  addUser(req.body);
  res.status([1]).send('User created');
});

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

A400

B201

C200

D404

Attempts:

3 left

💡 Hint

Common Mistakes

Using 200 which means OK but not specifically creation.

201 status code means a new resource was successfully created on the server.

4fill in blank

hard

Fill both blanks to send a 400 Bad Request status with a JSON error message.

Express

app.post('/login', (req, res) => {
  if (!req.body.username) {
    res.status([1]).json({ error: '[2]' });
  }
});

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

A400

B401

CBad Request

DUnauthorized

Attempts:

3 left

💡 Hint

Common Mistakes

Using 401 which means unauthorized, not bad request.

400 status means the client sent a bad request. The message 'Bad Request' explains the error.

5fill in blank

hard

Fill all three blanks to send a 500 Internal Server Error with a JSON message and end the response.

Express

app.get('/data', (req, res) => {
  try {
    const data = getData();
    res.json(data);
  } catch (error) {
    res.status([1]).json({ message: '[2]' }).[3]();
  }
});

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

A400

BInternal Server Error

Cend

D500

Attempts:

3 left

💡 Hint

Common Mistakes

Using 400 which means client error, not server error.

500 means a server error occurred. The message explains it. Calling end() finishes the response.

Practice

1. In Express, which status code is conventionally used to indicate a successful GET request?

easy

A. 301 Moved Permanently

B. 404 Not Found

C. 500 Internal Server Error

D. 200 OK

Solution

1. Step 1: Understand HTTP status codes for success

   The status code 200 means the request was successful and the server returned the requested data.

2. Step 2: Match the code to the GET request success

   For a successful GET request, 200 OK is the standard code to indicate success.

3. Final Answer:

   200 OK -> Option D

4. Quick Check:

   Success code for GET = 200 OK [OK]

Hint: 200 means success, use it for successful GET requests [OK]

Common Mistakes:

• Using 404 for success
• Using 500 for client errors
• Confusing 301 with success

2. Which of the following is the correct way to set a 404 status code in Express?

easy

A. res.statusCode = 404; res.send('Not Found')

B. res.sendStatus(200)

C. res.status(404).send('Not Found')

D. res.code(404).send('Not Found')

Solution

1. Step 1: Recall Express method to set status code

   Express uses res.status(code) to set the HTTP status code before sending a response.

2. Step 2: Verify correct syntax for 404

   res.status(404).send('Not Found') correctly sets status 404 and sends the message.

3. Final Answer:

   res.status(404).send('Not Found') -> Option C

4. Quick Check:

   Use res.status(code) to set status [OK]

Hint: Use res.status(code) before send() to set status [OK]

Common Mistakes:

• Using res.code() which doesn't exist
• Setting res.statusCode directly without chaining
• Using sendStatus(200) for 404

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

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

medium

A. 201 Created

B. 404 Not Found

C. 200 OK

D. 500 Internal Server Error

Solution

1. Step 1: Identify the status code set in the code

   The code uses res.status(201) which sets the HTTP status code to 201.

2. Step 2: Understand the meaning of 201

   Status 201 means the request was successful and a new resource was created.

3. Final Answer:

   201 Created -> Option A

4. Quick Check:

   res.status(201) sends 201 Created [OK]

Hint: res.status(201) means resource created successfully [OK]

Common Mistakes:

• Assuming default 200 status
• Confusing 201 with 404
• Ignoring the status() call

4. You wrote this Express code but clients always get status 200 instead of 400:

app.post('/submit', (req, res) => {
  if (!req.body.name) {
    res.status(400);
    res.send('Name is required');
  }
});

What is the main problem?

medium

A. res.send() must come before res.status()

B. res.status(400) must be followed by return to stop execution

C. 400 is not a valid status code

D. res.status() does not set the status code

Solution

1. Step 1: Analyze the code flow after setting status 400

   res.status(400) sets the status but code continues to run after sending response.

2. Step 2: Understand Express response behavior

   Without return, Express may continue and send default 200 later or cause errors.

3. Final Answer:

   res.status(400) must be followed by return to stop execution -> Option B

4. Quick Check:

   Use return after res.status().send() to stop further processing [OK]

Hint: Add return after res.status().send() to prevent default 200 [OK]

Common Mistakes:

• Not returning after sending response
• Calling res.send() before res.status()
• Thinking 400 is invalid

5. You want to send a 204 No Content status after deleting a resource in Express. Which code snippet correctly does this?

hard

A. res.status(204).send()

B. res.sendStatus(204).send('Deleted')

C. res.status(204).send('Deleted')

D. res.send(204)

Solution

1. Step 1: Understand 204 No Content meaning

   204 means success but no response body should be sent.

2. Step 2: Choose code that sends 204 without content

   res.status(204).send() sends status 204 with empty body, which is correct.

3. Step 3: Identify incorrect options

   res.sendStatus(204).send('Deleted') tries to chain send() after sendStatus(), which is invalid. res.status(204).send('Deleted') sends a body with 204, which breaks the rule. res.send(204) sends 204 as body, not status.

4. Final Answer:

   res.status(204).send() -> Option A

5. Quick Check:

   204 means no content, so send empty response [OK]

Hint: Use res.status(204).send() to send no content response [OK]

Common Mistakes:

• Sending body with 204 status
• Using sendStatus(204).send()
• Sending status code as body