res.status for status codes in Express - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What does res.status(404).send('Not Found') do?

In an Express app, what is the effect of calling res.status(404).send('Not Found') inside a route handler?

Express

app.get('/item', (req, res) => {
  res.status(404).send('Not Found');
});

A Sends a response with HTTP status 200 and body 'Not Found'.

B Throws an error and crashes the server.

C Sends a response with HTTP status 404 but no body.

D Sends a response with HTTP status 404 and body 'Not Found'.

💡 Hint

Think about what res.status() sets and what send() does.

The res.status(404) sets the HTTP status code to 404. The send('Not Found') sends the response body with that status. So the client gets a 404 status and the text 'Not Found'.

📝 Syntax

intermediate

Which option correctly sets status 201 and sends JSON data?

Choose the correct Express code to send a 201 status with JSON {"success": true}.

A res.status(201).sendJson({success: true});

B res.send(201).json({success: true});

C res.status(201).json({success: true});

D res.status = 201; res.json({success: true});

💡 Hint

Remember the correct method to set status and send JSON.

res.status(201) sets the status code. json() sends JSON data. Option C uses both correctly.

🔧 Debug

advanced

Why does res.status(500).send() send a blank response?

In Express, what happens if you call res.status(500).send() without any argument?

Express

app.get('/error', (req, res) => {
  res.status(500).send();
});

A It throws a TypeError because send() needs an argument.

B It sends a 500 status with an empty body.

C It sends a 500 status with the default error message.

D It sends a 200 status with an empty body.

💡 Hint

Check what happens when send() is called with no argument.

Calling send() without arguments sends an empty response body but keeps the status code set by res.status(500).

❓ state_output

advanced

What is the status code after res.status(200).status(404).send('Oops')?

Consider this Express code snippet:

res.status(200).status(404).send('Oops');

What status code will the client receive?

A 404

B 200

C 500

D It causes an error and no response is sent.

💡 Hint

Think about method chaining and which status code is last set.

The last status(404) call overrides the previous status(200). So the response status is 404.

🧠 Conceptual

expert

Which status code is most appropriate for a successful resource creation?

In REST APIs using Express, which HTTP status code should you set with res.status() when a new resource is successfully created?

A 201

B 200

C 204

D 400

💡 Hint

Think about the standard HTTP codes for resource creation.

Status 201 means 'Created' and is the standard code to indicate successful creation of a resource.

Practice

1. What does res.status(404) do in an Express route handler?

easy

A. Changes the request method to GET

B. Sends a 404 error message to the client automatically

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

D. Stops the server from running

Solution

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

   res.status(code) sets the HTTP status code for the response but does not send the response itself.

2. Step 2: Identify what 404 means

   404 is the standard HTTP status code meaning "Not Found".

3. Final Answer:

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

4. Quick Check:

   res.status(404) = sets status code 404 [OK]

Hint: res.status sets code; use res.send or res.json to send [OK]

Common Mistakes:

• Thinking res.status sends the response automatically
• Confusing status code with request method
• Assuming res.status stops server execution

2. Which of the following is the correct way to send a 201 status with a JSON response in Express?

easy

A. res.status.json(201, { message: 'Created' })

B. res.send(201).json({ message: 'Created' })

C. res.json(201, { message: 'Created' })

D. res.status(201).json({ message: 'Created' })

Solution

1. Step 1: Recall correct chaining syntax

   In Express, res.status(code) sets the status code, then res.json(data) sends the JSON response.

2. Step 2: Check each option's syntax

   res.status(201).json({ message: 'Created' }) correctly chains res.status(201) with res.json({ message: 'Created' }). Others misuse method order or parameters.

3. Final Answer:

   res.status(201).json({ message: 'Created' }) -> Option D

4. Quick Check:

   Correct chaining = res.status().json() [OK]

Hint: Use res.status(code).json(data) to set code and send JSON [OK]

Common Mistakes:

• Calling res.send before res.status
• Passing status code as first argument to res.json
• Using res.status.json which is invalid

3. What will the client receive when this Express handler runs?

app.get('/test', (req, res) => {
  res.status(500);
  res.send('Server error');
});

medium

A. A response with status 200 and body 'Server error'

B. A response with status 500 and body 'Server error'

C. A response with status 500 and empty body

D. An error thrown by Express

Solution

1. Step 1: Analyze res.status and res.send usage

   res.status(500) sets the HTTP status code to 500. Then res.send('Server error') sends the response body with that status.

2. Step 2: Determine final response

   The client receives status 500 with the text 'Server error' as the body.

3. Final Answer:

   A response with status 500 and body 'Server error' -> Option B

4. Quick Check:

   res.status(500) + res.send('Server error') = 500 + body [OK]

Hint: res.status sets code; res.send sends body with that code [OK]

Common Mistakes:

• Assuming res.send resets status to 200
• Thinking status 500 causes Express error automatically
• Believing response body is empty without res.send argument

4. Identify the error in this Express code snippet:

app.get('/error', (req, res) => {
  res.send('Oops!');
  res.status(400);
});

medium

A. res.status(400) is called after res.send, so status code is ignored

B. res.send cannot be called without res.status first

C. res.status must be called with a string, not a number

D. No error, this code works correctly

Solution

1. Step 1: Understand response flow in Express

   Once res.send() is called, the response is sent and closed. Any code after it won't affect the response.

2. Step 2: Analyze order of calls

   Here, res.send('Oops!') sends the response with default status 200. Then res.status(400) is called but ignored because response is already sent.

3. Final Answer:

   res.status(400) is called after res.send, so status code is ignored -> Option A

4. Quick Check:

   Call res.status before res.send to set status [OK]

Hint: Always call res.status before res.send or res.json [OK]

Common Mistakes:

• Calling res.status after res.send expecting status change
• Thinking res.send requires res.status first
• Using string instead of number in res.status

5. You want to send a 204 No Content status with no response body in Express. Which code snippet correctly does this?

hard

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

B. All of the above

C. res.status(204).json(null)

D. res.sendStatus(204)

Solution

1. Step 1: Understand 204 No Content meaning

   Status 204 means the server successfully processed the request but returns no content in the response body (Content-Length: 0).

2. Step 2: Check each option's behavior

   res.status(204).send() sends status 204 with empty body [check].
   res.status(204).json(null) sends status 204 with JSON "null" body ✗.
   res.sendStatus(204) sends status 204 with "No Content" text body ✗.
   Only A sends no response body.

3. Final Answer:

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

4. Quick Check:

   res.status(204).send() = 204 + empty body [OK]

Hint: Use res.status(204).send() for 204 with no body [OK]

Common Mistakes:

• Sending body content with 204 status (should be empty)
• Using res.status(204).json({}) which sends empty object body
• Not sending response after setting status