req.method and req.url in Express - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What does this Express handler log for a GET request to /home?

Consider this Express.js route handler:

app.use((req, res) => { console.log(req.method, req.url); res.end('done'); });

What will be logged if a client sends a GET request to /home?

Express

app.use((req, res) => { console.log(req.method, req.url); res.end('done'); });

A "GET /"

B "POST /home"

C "GET /home"

D "POST /"

💡 Hint

Remember, req.method is the HTTP method used, and req.url is the path requested.

The req.method property holds the HTTP method, here 'GET'. The req.url property holds the path, here '/home'. So the console logs "GET /home".

📝 Syntax

intermediate

Which option correctly accesses the HTTP method and URL in Express?

You want to log the HTTP method and URL of a request in Express. Which code snippet is correct?

A console.log(req.method, req.url);

B console.log(req.Method, req.Url);

C console.log(req.method(), req.url());

D console.log(req['method'], req['url']);

💡 Hint

Check the exact property names and whether they are functions or properties.

In Express, req.method and req.url are properties, not functions, and are lowercase. Option A uses correct casing and syntax.

❓ state_output

advanced

What is the value of req.url after a request to /api/items?sort=asc

If a client sends a GET request to /api/items?sort=asc, what will req.url contain in Express?

A "/api/items?sort=asc"

B "/api/items"

C "sort=asc"

D "/api/items/?sort=asc"

💡 Hint

req.url includes the path and the query string exactly as sent.

req.url contains the full path and query string, so it includes '?sort=asc'.

🔧 Debug

advanced

Why does this code log 'undefined undefined' for req.method and req.url?

Look at this Express middleware:

app.use((request, response) => { console.log(req.method, req.url); response.end('ok'); });

Why does it log 'undefined undefined'?

Express

app.use((request, response) => { console.log(req.method, req.url); response.end('ok'); });

A Because req.method and req.url are not valid properties in Express.

B Because the parameter names are 'request' and 'response', but 'req' is used inside the function.

C Because response.end() must be called before logging.

D Because app.use does not receive req and res parameters.

💡 Hint

Check the variable names used inside the function vs parameters.

The function parameters are named 'request' and 'response', but the code uses 'req' which is undefined, so req.method and req.url are undefined.

🧠 Conceptual

expert

How does Express determine req.url when using a router mounted at a path?

Suppose you mount a router at /api like this:

app.use('/api', router);

Inside the router, what does req.url represent when a request is made to /api/users?

A It contains only the query string part, if any.

B It contains the full original URL, so '/api/users'.

C It is always '/' inside routers.

D It contains the path relative to the mount point, so '/users'.

💡 Hint

Think about how Express routers handle paths relative to where they are mounted.

Inside a router mounted at '/api', req.url is the path relative to '/api', so for '/api/users' it is '/users'.

Practice

1. What does req.method represent in an Express request?

easy

A. The HTTP method used by the client (e.g., GET, POST)

B. The full URL including domain name

C. The IP address of the client

D. The server's response status code

Solution

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

   req.method holds the HTTP method used by the client to make the request, such as GET, POST, PUT, DELETE.

2. Step 2: Differentiate from other request properties

   req.url gives the path and query, IP address is separate, and response status is not part of the request object.

3. Final Answer:

   The HTTP method used by the client (e.g., GET, POST) -> Option A

4. Quick Check:

   req.method = HTTP method [OK]

Hint: Remember: method means action type like GET or POST [OK]

Common Mistakes:

• Confusing req.method with req.url
• Thinking req.method gives client IP
• Assuming req.method is server response code

2. Which of the following is the correct way to check if a request is a POST method in Express?

easy

A. if (req.url === 'POST')

B. if (req.url === '/post')

C. if (req.method = 'POST')

D. if (req.method === 'POST')

Solution

1. Step 1: Identify the property holding HTTP method

   The HTTP method is stored in req.method, so we compare it to the string 'POST'.

2. Step 2: Check syntax correctness

   if (req.method === 'POST') uses strict equality (===) to compare req.method to 'POST', which is correct. if (req.method = 'POST') uses assignment (=) which is wrong.

3. Final Answer:

   if (req.method === 'POST') -> Option D

4. Quick Check:

   Check req.method with === 'POST' [OK]

Hint: Use === to compare req.method with 'POST' string [OK]

Common Mistakes:

• Using assignment (=) instead of comparison (===)
• Checking req.url instead of req.method
• Comparing req.method to lowercase 'post'

3. Given this Express code snippet, what will be logged if a client sends a GET request to /home?user=123?

app.use((req, res, next) => {
  console.log(req.method);
  console.log(req.url);
  next();
});

medium

A. GET
/home?user=123

B. POST
/home?user=123

C. GET
/home

D. POST
/home

Solution

1. Step 1: Identify the HTTP method from the request

   The client sends a GET request, so req.method will be 'GET'.

2. Step 2: Identify the URL including query string

   req.url includes the path and query string, so it will be '/home?user=123'.

3. Final Answer:

   GET /home?user=123 -> Option A

4. Quick Check:

   req.method = GET, req.url includes query [OK]

Hint: req.url includes path plus query string [OK]

Common Mistakes:

• Ignoring query string in req.url
• Assuming req.method is POST by default
• Confusing req.url with just the path

4. What is wrong with this Express middleware code if it aims to log only POST requests?

app.use((req, res, next) => {
  if (req.method = 'POST') {
    console.log('POST request received');
  }
  next();
});

medium

A. Missing parentheses around req.method

B. Using assignment (=) instead of comparison (===) in the if condition

C. Logging message is incorrect

D. next() is called before the if condition

Solution

1. Step 1: Check the if condition syntax

   The condition uses = which assigns 'POST' to req.method instead of comparing it. This causes a bug.

2. Step 2: Identify correct comparison operator

   Use === to compare values in JavaScript, so the condition should be req.method === 'POST'.

3. Final Answer:

   Using assignment (=) instead of comparison (===) in the if condition -> Option B

4. Quick Check:

   Use === for comparison, not = [OK]

Hint: Use === to compare, not = which assigns [OK]

Common Mistakes:

• Using = instead of === in if condition
• Thinking next() must be before if
• Assuming parentheses needed around req.method

5. You want to create an Express middleware that logs a message only when the client requests the URL /api/data with a GET method. Which code snippet correctly implements this?

hard

A. app.use((req, res, next) => {
if (req.method === 'POST' && req.url === '/api/data') {
console.log('GET request to /api/data');
}
next();
});

B. app.use((req, res, next) => {
if (req.method = 'GET' || req.url === '/api/data') {
console.log('GET request to /api/data');
}
next();
});

C. app.use((req, res, next) => {
if (req.method === 'GET' && req.url === '/api/data') {
console.log('GET request to /api/data');
}
next();
});

D. app.use((req, res, next) => {
if (req.method === 'GET' && req.url === '/api') {
console.log('GET request to /api/data');
}
next();
});

Solution

1. Step 1: Check method and URL conditions

   The middleware should check if req.method is exactly 'GET' and req.url is exactly '/api/data'.

2. Step 2: Verify logical operators and syntax

   app.use((req, res, next) => { if (req.method === 'GET' && req.url === '/api/data') { console.log('GET request to /api/data'); } next(); }); uses strict equality (===) and logical AND (&&) correctly. app.use((req, res, next) => { if (req.method = 'GET' || req.url === '/api/data') { console.log('GET request to /api/data'); } next(); }); uses assignment (=) and OR (||) which is wrong. Options C and D check wrong method or URL.

3. Final Answer:

   app.use((req, res, next) => { if (req.method === 'GET' && req.url === '/api/data') { console.log('GET request to /api/data'); } next(); }); -> Option C

4. Quick Check:

   Check req.method === 'GET' AND req.url === '/api/data' [OK]

Hint: Use === and && to check method and exact URL [OK]

Common Mistakes:

• Using = instead of ===
• Using || instead of &&
• Checking wrong URL or method