req.method and req.url in Express - Mini Project: Build & Apply

Using req.method and req.url in Express

📖 Scenario: You are building a simple Express server that logs the HTTP method and URL of incoming requests. This helps you understand what requests your server receives.

🎯 Goal: Create an Express server that listens on port 3000 and logs the req.method and req.url for every request.

📋 What You'll Learn

Create an Express app using express()

Use app.use to add a middleware that logs req.method and req.url

Start the server listening on port 3000

Use exact variable names: app, req, res, next

💡 Why This Matters

🌍 Real World

Logging request methods and URLs helps developers monitor and debug web servers by seeing what requests come in.

💼 Career

Understanding req.method and req.url is essential for backend developers working with Express to handle routing and middleware.

1

Setup Express app

Create a variable called express that requires the 'express' module. Then create a variable called app by calling express().

Express

const express = require('express');
const app = express();
// Your code here

Hint

Use require('express') to import Express and then call it to create the app.

2

Add logging middleware

Use app.use to add a middleware function with parameters req, res, and next. Inside it, write a line that logs req.method and req.url using console.log. Then call next().

Express

const express = require('express');
const app = express();

// Add middleware to log req.method and req.url
app.use((req, res, next) => {
  // Your code here
});

Hint

The middleware function receives req, res, and next. Use console.log(req.method, req.url) to log the method and URL.

3

Add a simple route

Add a GET route for path '/' using app.get. The handler function should take req and res and respond with res.send('Hello World').

Express

const express = require('express');
const app = express();

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

// Add GET route for '/' here
app.get('/', (req, res) => {
  // Your code here
});

Hint

Use app.get to create a route for '/' that sends back 'Hello World'.

4

Start the server

Use app.listen to start the server on port 3000. The callback function should log 'Server running on port 3000'.

Express

const express = require('express');
const app = express();

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

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

// Start server on port 3000
app.listen(3000, () => {
  // Your code here
});

Hint

Use app.listen(3000, () => { console.log(...) }) to start the server and log a message.

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