res.send for general responses in Express - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What does this Express code send to the client?

Consider this Express route handler:

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

What will the client receive when requesting /hello?

Express

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

A A redirect to '/hello/world'

B The string 'Hello World!' as the response body with status 200

C An empty response with status 204

D A JSON object { message: 'Hello World!' }

💡 Hint

res.send sends the exact data you give it as the response body.

The res.send method sends the string 'Hello World!' as the response body with HTTP status 200 by default.

📝 Syntax

intermediate

Which option correctly sends a JSON response using res.send?

You want to send this JSON object as a response:

{ success: true, data: [1, 2, 3] }

Which code correctly sends it using res.send?

A res.send('success: true, data: [1, 2, 3]');

B res.send(JSON.stringify({ success: true, data: [1, 2, 3] }));

C res.send({ success: true, data: [1, 2, 3] });

D res.send({ 'success': 'true', 'data': '[1, 2, 3]' });

💡 Hint

res.send can accept an object and automatically sends JSON.

Passing an object to res.send automatically converts it to JSON and sets the Content-Type header.

🔧 Debug

advanced

Why does this code cause an error?

Look at this Express handler:

app.get('/test', (req, res) => { res.send(123); res.send('Done'); });

What error or behavior will happen when a client requests /test?

Express

app.get('/test', (req, res) => { res.send(123); res.send('Done'); });

A Error: Cannot set headers after they are sent to the client

B The client receives '123Done' as a combined response

C The client receives only 'Done' as the response

D The server crashes with a syntax error

💡 Hint

You can only send one response per request.

Calling res.send twice causes an error because headers and body can only be sent once per request.

❓ state_output

advanced

What is the Content-Type header when sending a number with res.send?

Given this code:

app.get('/number', (req, res) => { res.send(42); });

What Content-Type header will the client receive?

Express

app.get('/number', (req, res) => { res.send(42); });

A No Content-Type header is sent

B application/json; charset=utf-8

C text/plain; charset=utf-8

D text/html; charset=utf-8

💡 Hint

Numbers are converted to strings when sent.

Sending a number with res.send converts it to a string and sets Content-Type to text/html; charset=utf-8.

🧠 Conceptual

expert

Which statement about res.send behavior is true?

Choose the correct statement about how res.send works in Express:

A res.send ends the response process and cannot be called multiple times per request

B res.send buffers the entire response before sending it to the client

C res.send automatically sets Content-Type to application/json when sending objects

D res.send can only send strings and buffers, not objects or numbers

💡 Hint

Think about what happens after res.send is called.

res.send ends the response and calling it again causes an error; it can send strings, buffers, numbers, and objects (converted to JSON).