req.ip and req.hostname in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to get the client's IP address using Express.

Express

app.get('/client-ip', (req, res) => {
  const clientIp = req.[1];
  res.send(`Client IP is: ${clientIp}`);
});

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

Aip

Bhostname

Cpath

Durl

Attempts:

3 left

💡 Hint

Common Mistakes

Using req.hostname instead of req.ip

Trying to access req.url for IP

The req.ip property in Express gives the client's IP address.

2fill in blank

medium

Complete the code to get the hostname from the request in Express.

Express

app.get('/host', (req, res) => {
  const hostName = req.[1];
  res.send(`Hostname is: ${hostName}`);
});

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

Ahostname

Bip

Cprotocol

Dmethod

Attempts:

3 left

💡 Hint

Common Mistakes

Using req.ip instead of req.hostname

Using req.protocol to get hostname

The req.hostname property gives the hostname from the request.

3fill in blank

hard

Fix the error in accessing the client's IP address in this Express route.

Express

app.get('/fix-ip', (req, res) => {
  const clientIp = req.[1];
  res.send(`IP: ${clientIp}`);
});

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

AgetIp

Bhostname

Cip

DipAddress

Attempts:

3 left

💡 Hint

Common Mistakes

Calling req.ip as a function

Using non-existent methods like req.getIp()

req.ip is a property, not a function, so no parentheses are needed.

4fill in blank

hard

Fill both blanks to create a route that sends both IP and hostname.

Express

app.get('/info', (req, res) => {
  const ip = req.[1];
  const host = req.[2];
  res.send(`IP: ${ip}, Hostname: ${host}`);
});

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

Aip

Bhostname

Curl

Dmethod

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping ip and hostname properties

Using req.url or req.method instead

Use req.ip for IP and req.hostname for hostname.

5fill in blank

hard

Fill all three blanks to log IP, hostname, and request method in Express.

Express

app.use((req, res, next) => {
  console.log('IP:', req.[1]);
  console.log('Host:', req.[2]);
  console.log('Method:', req.[3]);
  next();
});

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

Aip

Bhostname

Cmethod

Durl

Attempts:

3 left

💡 Hint

Common Mistakes

Using req.url instead of req.method

Mixing up hostname and url

Use req.ip for IP, req.hostname for hostname, and req.method for HTTP method.

Practice

1. What does req.ip represent in an Express app?

easy

A. The visitor's IP address

B. The domain name used in the request

C. The server's IP address

D. The HTTP method of the request

Solution

1. Step 1: Understand the purpose of req.ip

   req.ip provides the IP address of the client making the request.

2. Step 2: Differentiate from req.hostname

   req.hostname gives the domain name, not the IP address.

3. Final Answer:

   The visitor's IP address -> Option A

4. Quick Check:

   req.ip = visitor's IP [OK]

Hint: Remember: IP is address, hostname is domain name [OK]

Common Mistakes:

• Confusing req.ip with req.hostname
• Thinking req.ip is server IP
• Assuming req.ip gives HTTP method

2. Which of the following is the correct way to access the hostname in an Express route handler?

easy

A. req.host

B. req.domain

C. req.hostname

D. req.hostName

Solution

1. Step 1: Recall Express request object properties

   The correct property for the domain name is req.hostname.

2. Step 2: Check other options for validity

   req.host, req.domain, and req.hostName are not valid Express properties.

3. Final Answer:

   req.hostname -> Option C

4. Quick Check:

   Hostname property = req.hostname [OK]

Hint: Hostname is all lowercase: req.hostname [OK]

Common Mistakes:

• Using req.host instead of req.hostname
• Capitalizing property names incorrectly
• Assuming req.domain exists

3. Consider this Express route handler: <pre>app.get('/', (req, res) => { res.send(`IP: ${req.ip}, Hostname: ${req.hostname}`); }); If a user visits http://example.com from IP 192.168.1.5, what will be the response text?

medium

A. IP: undefined, Hostname: example.com

B. IP: example.com, Hostname: 192.168.1.5

C. IP: 127.0.0.1, Hostname: localhost

D. IP: 192.168.1.5, Hostname: example.com

Solution

1. Step 1: Identify req.ip and req.hostname values

   req.ip gives the visitor's IP, which is 192.168.1.5. req.hostname gives the domain, which is example.com.

2. Step 2: Substitute values into the response string

   The response string becomes: IP: 192.168.1.5, Hostname: example.com.

3. Final Answer:

   IP: 192.168.1.5, Hostname: example.com -> Option D

4. Quick Check:

   IP and hostname match request info [OK]

Hint: Match IP to visitor, hostname to domain in response [OK]

Common Mistakes:

• Swapping IP and hostname values
• Assuming localhost IP instead of visitor IP
• Using undefined or wrong properties

4. You wrote this Express middleware: <pre>app.use((req, res, next) => { console.log(req.ipAddress); next(); }); What is the problem with this code?

medium

A. Middleware must be declared after routes

B. req.ipAddress is not a valid property; should use req.ip

C. Logging should be done with res.ip instead

D. Missing call to next() to continue middleware chain

Solution

1. Step 1: Check property names on req

   req.ipAddress does not exist in Express; the correct property is req.ip.

2. Step 2: Verify middleware correctness

   The middleware calls next(), so chain continues correctly.

3. Final Answer:

   req.ipAddress is not a valid property; should use req.ip -> Option B

4. Quick Check:

   Use req.ip for IP address [OK]

Hint: Use exact property names: IP is req.ip [OK]

Common Mistakes:

• Using req.ipAddress instead of req.ip
• Forgetting to call next()
• Trying to log IP from res object

5. You want to restrict access to your Express app only to requests coming from the domain trusted.com. Which code snippet correctly uses req.hostname to allow this?

hard

A. app.use((req, res, next) => { if (req.hostname === 'trusted.com') next(); else res.status(403).send('Forbidden'); });

B. app.use((req, res, next) => { if (req.ip === 'trusted.com') next(); else res.status(403).send('Forbidden'); });

C. app.use((req, res, next) => { if (req.host === 'trusted.com') next(); else res.status(403).send('Forbidden'); });

D. app.use((req, res, next) => { if (req.hostname.includes('trusted.com')) next(); else res.status(403).send('Forbidden'); });

Solution

1. Step 1: Use req.hostname to check exact domain

   app.use((req, res, next) => { if (req.hostname === 'trusted.com') next(); else res.status(403).send('Forbidden'); }); correctly compares req.hostname to the string 'trusted.com'.

2. Step 2: Evaluate other options for correctness

   app.use((req, res, next) => { if (req.ip === 'trusted.com') next(); else res.status(403).send('Forbidden'); }); wrongly compares req.ip to a domain string. app.use((req, res, next) => { if (req.host === 'trusted.com') next(); else res.status(403).send('Forbidden'); }); uses invalid req.host. app.use((req, res, next) => { if (req.hostname.includes('trusted.com')) next(); else res.status(403).send('Forbidden'); }); uses includes which may allow subdomains, not exact match.

3. Final Answer:

   Option A code snippet -> Option A

4. Quick Check:

   Exact match with req.hostname = app.use((req, res, next) => { if (req.hostname === 'trusted.com') next(); else res.status(403).send('Forbidden'); }); [OK]

Hint: Check exact domain with req.hostname === 'domain' [OK]

Common Mistakes:

• Comparing IP to domain string
• Using invalid property req.host
• Using partial match instead of exact domain