res.send for general responses in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to send a simple text response using Express.

Express

app.get('/', (req, res) => { res.[1]('Hello World!'); });

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

Asend

Bwrite

Cjson

Drender

Attempts:

3 left

💡 Hint

Common Mistakes

Using res.write which is not a method in Express response object.

Using res.json which sends JSON, not plain text.

Using res.render which is for templates.

The res.send method sends a simple response to the client. It can send strings, buffers, or objects.

2fill in blank

medium

Complete the code to send a JSON response using Express.

Express

app.get('/data', (req, res) => { res.[1]({ message: 'Success' }); });

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

Aend

Bsend

Cwrite

Djson

Attempts:

3 left

💡 Hint

Common Mistakes

Using res.send with an object, which works but does not explicitly set JSON headers.

Using res.end which just ends the response without sending data.

Using res.write which is not an Express method.

The res.json method sends a JSON response. It automatically sets the Content-Type header to application/json.

3fill in blank

hard

Fix the error in sending a response with status 404 and a message.

Express

app.get('/notfound', (req, res) => { res.status(404).[1]('Page not found'); });

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

Ajson

Bsend

Cwrite

Drender

Attempts:

3 left

💡 Hint

Common Mistakes

Using res.write which is not an Express method.

Using res.render which is for templates, not plain text.

Using res.json which sends JSON, but here a simple text message is expected.

To send a status code with a message, chain res.status() with res.send(). The res.send method sends the response body.

4fill in blank

hard

Fill both blanks to send a JSON response with status 201 and a message.

Express

app.post('/create', (req, res) => { res.[1](201).[2]({ success: true }); });

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

Astatus

Bsend

Cjson

Dend

Attempts:

3 left

💡 Hint

Common Mistakes

Using res.send instead of res.json for JSON data.

Using res.end which does not send data.

Not chaining methods properly.

First set the status code with res.status(), then send JSON data with res.json().

5fill in blank

hard

Fill the blanks to send a plain text response with status 500 and a custom message.

Express

app.get('/error', (req, res) => { res.[1](500).[2]('Error: Something went wrong'); });

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

Astatus

Bsend

Cwrite

Djson

Attempts:

3 left

💡 Hint

Common Mistakes

Using res.write which is not an Express method.

Using res.json which sends JSON, not plain text.

Not chaining the status and send methods.

Set the status with res.status(), then send the plain text message using res.send().

Practice

1. What does res.send() do in an Express app?

easy

A. Logs information to the console

B. Sends a response back to the client and ends the request

C. Reads data from the client request

D. Starts a new server

Solution

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

   res.send() is used to send a response back to the client in Express.

2. Step 2: Recognize that it ends the response

   After sending data, res.send() automatically ends the response, so no more data is sent.

3. Final Answer:

   Sends a response back to the client and ends the request -> Option B

4. Quick Check:

   res.send() = sends response [OK]

Hint: Remember: res.send sends and finishes response [OK]

Common Mistakes:

• Thinking res.send starts the server
• Confusing res.send with reading request data
• Assuming res.send logs to console

2. Which of the following is the correct syntax to send a plain text response using res.send?

easy

A. res.send('Hello');

B. res.send[Hello];

C. res.send({ message: 'Hello' });

D. res.send = 'Hello';

Solution

1. Step 1: Identify correct method call syntax

   The correct way to call res.send is as a function with parentheses and the data inside.

2. Step 2: Check the options for valid syntax

   res.send('Hello'); uses res.send('Hello'); which is correct. res.send({ message: 'Hello' }); sends an object, which is valid but not plain text. Options B and D have invalid syntax.

3. Final Answer:

   res.send('Hello'); -> Option A

4. Quick Check:

   Correct function call = res.send('text') [OK]

Hint: Use parentheses and quotes: res.send('text') [OK]

Common Mistakes:

• Using square brackets instead of parentheses
• Assigning value instead of calling function
• Sending object when plain text is needed

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

app.get('/test', (req, res) => {
  res.send({ success: true });
});

medium

A. A plain text: '[object Object]'

B. Nothing, response is empty

C. An error because object can't be sent

D. A JSON string: '{"success":true}'

Solution

1. Step 1: Understand res.send with an object

   When res.send() receives an object, Express converts it to JSON automatically.

2. Step 2: Predict the client response

   The client will get a JSON string representing the object: '{"success":true}'.

3. Final Answer:

   A JSON string: '{"success":true}' -> Option D

4. Quick Check:

   res.send(object) = JSON string [OK]

Hint: Objects sent with res.send become JSON strings [OK]

Common Mistakes:

• Expecting plain text '[object Object]'
• Thinking it causes an error
• Assuming empty response

4. Identify the error in this Express route:

app.get('/hello', (req, res) => {
  res.send('Hello');
  res.send('Again');
});

medium

A. Calling res.send twice causes an error

B. Missing semicolon after res.send

C. res.send cannot send strings

D. Route path is invalid

Solution

1. Step 1: Check multiple res.send calls in one route

   Once res.send() is called, the response is finished and cannot be sent again.

2. Step 2: Understand the error caused

   Calling res.send() a second time causes an error because the response is already closed.

3. Final Answer:

   Calling res.send twice causes an error -> Option A

4. Quick Check:

   Only one res.send per response [OK]

Hint: Send response once; multiple res.send calls cause errors [OK]

Common Mistakes:

• Ignoring that response ends after first send
• Thinking multiple sends append data
• Blaming syntax or route path

5. You want to send a JSON response with a status code 201 and a message 'Created' using res.send. Which code correctly does this?

hard

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

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

C. res.status(201).send({ message: 'Created' });

D. res.status(201).send('Created');

Solution

1. Step 1: Set status code before sending response

   Use res.status(201) to set the HTTP status code to 201.

2. Step 2: Send JSON object with message

   Chain .send({ message: 'Created' }) to send the JSON response.

3. Final Answer:

   res.status(201).send({ message: 'Created' }); -> Option C

4. Quick Check:

   Status then send JSON = res.status(201).send({ message: 'Created' }); [OK]

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

Common Mistakes:

• Passing status code as first argument to send
• Sending status inside JSON instead of HTTP status
• Sending plain text when JSON is needed