Node.js Express Request and Response Practice Questions with Solutions

Introduction

The request and response objects are at the heart of Express.js applications. The req object contains information sent by the client, while the res object is used by the server to send data back. In this chapter, you will practice req and res with 10 solved examples covering request methods, URLs, parameters, query strings, request bodies, headers, JSON responses, status codes, redirects, and practical API responses. Node.js Express Request and Response Practice questions with solutions help to understand the concepts.

Question 1: How do you read the HTTP method from the request object?

Problem

Create an Express application that displays the HTTP method used by the client.

Solution

const express = require("express");

const app = express();

app.use((req, res) => {

    res.send(`HTTP Method: ${req.method}`);

});

app.listen(3000, () => {

    console.log(
        "Server running on http://localhost:3000"
    );

});

Test

Open:

http://localhost:3000/

Output

HTTP Method: GET

Step-by-Step Explanation

The request object is represented by:

req

Express provides the HTTP method through:

req.method

When you open a webpage in a browser, the browser normally sends a GET request.

Therefore:

req.method

returns:

GET

Question 2: How do you read the requested URL?

Problem

Create a route that displays the URL requested by the client.

Solution

const express = require("express");

const app = express();

app.get("/about", (req, res) => {

    res.send(`Requested URL: ${req.url}`);

});

app.listen(3000, () => {

    console.log(
        "Server running on http://localhost:3000"
    );

});

Test

Open:

http://localhost:3000/about

Output

Requested URL: /about

Step-by-Step Explanation

Express provides the requested URL through:

req.url

For example, if the client requests:

/about

then:

req.url

contains:

/about

Question 3: How do you read route parameters from the request?

Problem

Create a student route that accepts a student ID from the URL.

Solution

const express = require("express");

const app = express();

app.get("/students/:id", (req, res) => {

    const studentId = req.params.id;

    res.send(
        `Student ID is: ${studentId}`
    );

});

app.listen(3000, () => {

    console.log(
        "Server running on http://localhost:3000"
    );

});

Test

Open:

http://localhost:3000/students/25

Output

Student ID is: 25

Step-by-Step Explanation

The route contains:

/students/:id

Here, :id is a route parameter.

Express stores route parameters inside:

req.params

Therefore:

req.params.id

gets the ID.

For:

/students/25

the value is:

Question 4: How do you read query parameters from the request?

Problem

Create a search route that reads name and course from the query string.

Solution

const express = require("express");

const app = express();

app.get("/search", (req, res) => {

    const name = req.query.name;
    const course = req.query.course;

    res.json({
        name: name,
        course: course
    });

});

app.listen(3000, () => {

    console.log(
        "Server running on http://localhost:3000"
    );

});

Test

Open:

http://localhost:3000/search?name=Rahul&amp;course=Node.js

Output

{
    "name": "Rahul",
    "course": "Node.js"
}

Step-by-Step Explanation

The query string is:

?name=Rahul&course=Node.js

Express makes query parameters available through:

req.query

Therefore:

req.query.name

returns:

Rahul

And:

req.query.course

returns:

Node.js

Question 5: How do you read JSON data from the request body?

Problem

Create a POST route that receives a student’s name and course in JSON format.

Solution

const express = require("express");

const app = express();

app.use(express.json());

app.post("/students", (req, res) => {

    const name = req.body.name;
    const course = req.body.course;

    res.json({
        message: "Student data received.",
        name: name,
        course: course
    });

});

app.listen(3000, () => {

    console.log(
        "Server running on http://localhost:3000"
    );

});

Send This JSON

{
    "name": "Aman",
    "course": "Python"
}

Output

{
    "message": "Student data received.",
    "name": "Aman",
    "course": "Python"
}

Step-by-Step Explanation

First, enable JSON parsing:

app.use(express.json());

Then the JSON data becomes available through:

req.body

For example:

req.body.name

gets the student’s name.

And:

req.body.course

gets the course.

Question 6: How do you read request headers?

Problem

Create a route that reads the User-Agent header sent by the client.

Solution

const express = require("express");

const app = express();

app.get("/", (req, res) => {

    const userAgent = req.get("User-Agent");

    res.send(
        `Your User-Agent is: ${userAgent}`
    );

});

app.listen(3000, () => {

    console.log(
        "Server running on http://localhost:3000"
    );

});

Test

Open:

http://localhost:3000/

The browser will display a User-Agent value similar to:

Your User-Agent is: Mozilla/5.0 ...

Step-by-Step Explanation

HTTP requests contain headers.

Express provides:

req.get()

for reading a specific request header.

This:

req.get("User-Agent")

reads the User-Agent header.

You can also read other headers:

req.get("Content-Type")

or:

req.get("Authorization")

Question 7: How do you send a JSON response using `res.json()`?

Problem

Create an API that returns student information as JSON.

Solution

const express = require("express");

const app = express();

app.get("/student", (req, res) => {

    const student = {
        id: 1,
        name: "Rahul",
        course: "Node.js"
    };

    res.json(student);

});

app.listen(3000, () => {

    console.log(
        "Server running on http://localhost:3000"
    );

});

Test

Open:

http://localhost:3000/student

Output

{
    "id": 1,
    "name": "Rahul",
    "course": "Node.js"
}

Step-by-Step Explanation

Create an object:

const student = {
    id: 1,
    name: "Rahul",
    course: "Node.js"
};

Then send it with:

res.json(student);

Express converts the JavaScript object into a JSON response.

Another Example

res.json({
    success: true,
    message: "Student found."
});

Question 8: How do you send an HTTP status code with a response?

Problem

Create an API that returns a 201 Created status when a student is successfully created.

Solution

const express = require("express");

const app = express();

app.use(express.json());

app.post("/students", (req, res) => {

    const student = {
        name: req.body.name,
        course: req.body.course
    };

    res.status(201).json({
        success: true,
        message: "Student created successfully.",
        student: student
    });

});

app.listen(3000, () => {

    console.log(
        "Server running on http://localhost:3000"
    );

});

Send

{
    "name": "Priya",
    "course": "JavaScript"
}

Response

{
    "success": true,
    "message": "Student created successfully.",
    "student": {
        "name": "Priya",
        "course": "JavaScript"
    }
}

The HTTP status is:

201 Created

Step-by-Step Explanation

This:

res.status(201)

sets the HTTP status code.

Then:

.json(...)

sends the JSON response.

You can combine them:

res.status(201).json({
    message: "Created"
});

Common Status Codes

Status	Meaning
200	Successful request
201	Resource created
400	Bad request
401	Authentication required
403	Forbidden
404	Resource not found
500	Server error

Question 9: How do you redirect a user using the response object?

Problem

Create an Express route that redirects the user from /old-page to /new-page.

Solution

const express = require("express");

const app = express();

app.get("/old-page", (req, res) => {

    res.redirect("/new-page");

});

app.get("/new-page", (req, res) => {

    res.send("Welcome to the New Page.");

});

app.listen(3000, () => {

    console.log(
        "Server running on http://localhost:3000"
    );

});

Test

Open:

http://localhost:3000/old-page

The browser will be redirected to:

http://localhost:3000/new-page

Output

Welcome to the New Page.

Step-by-Step Explanation

The old route uses:

res.redirect("/new-page");

Express tells the browser to go to another URL.

The new route then handles the request:

app.get("/new-page", ...)

Redirect to an External Website

You can also redirect to another website:

res.redirect("https://example.com");

Question 10: How do you combine request and response objects in a practical API?

Problem

Create a student API that reads:

Student ID from route parameters
Course from query parameters
Student name from JSON body
HTTP method from the request
A custom response using res.status() and res.json()

Solution

const express = require("express");

const app = express();

app.use(express.json());

app.post("/students/:id", (req, res) => {

    const studentId = req.params.id;

    const course = req.query.course;

    const name = req.body.name;

    const method = req.method;

    res.status(200).json({

        success: true,

        method: method,

        studentId: studentId,

        name: name,

        course: course

    });

});

app.listen(3000, () => {

    console.log(
        "Server running on http://localhost:3000"
    );

});

Send This Request

URL:

http://localhost:3000/students/25?course=Node.js

Method:

POST

JSON body:

{
    "name": "Rahul"
}

Response

{
    "success": true,
    "method": "POST",
    "studentId": "25",
    "name": "Rahul",
    "course": "Node.js"
}

Step-by-Step Explanation

The route is:

/students/:id

So the student ID comes from:

req.params.id

The URL also contains:

?course=Node.js

So the course comes from:

req.query.course

The JSON body contains:

{
    "name": "Rahul"
}

So the name comes from:

req.body.name

The HTTP method comes from:

req.method

Finally, the server sends the response using:

res.status(200).json(...)

Request and Response Flow

Client
   ↓
POST /students/25?course=Node.js
   ↓
Express
   ↓
req.params.id
req.query.course
req.body.name
req.method
   ↓
Route Handler
   ↓
res.status()
   ↓
res.json()
   ↓
Client

Key Takeaways

Express uses req to represent the incoming request.
Express uses res to represent the outgoing response.
req.method returns the HTTP method.
req.url provides the requested URL.
req.params contains route parameters.
req.query contains query parameters.
req.body contains parsed request body data.
express.json() is needed to parse JSON request bodies.
req.get() can read request headers.
res.send() sends a response to the client.
res.json() sends a JSON response.
res.status() sets the HTTP status code.
res.redirect() redirects the client to another URL.
req.params and req.query serve different purposes.
Route parameters are part of the URL path.
Query parameters appear after ? in the URL.
Request bodies are commonly used with POST and PUT/PATCH requests.
HTTP headers provide additional request information.
JSON responses are widely used in REST APIs.
Status codes communicate the result of a request.
A good Express API should return meaningful status codes.
req helps the server understand what the client sent.
res allows the server to control what the client receives.
Request and response objects are fundamental to Express.js development.

FAQs

1. What is the `req` object in Express.js?

The req object represents the incoming HTTP request.

It provides information such as:

req.method
req.url
req.params
req.query
req.body

For example:

app.get("/", (req, res) => {

    console.log(req.method);

});

The request object helps the server understand what the client requested.

2. What is the `res` object in Express.js?

The res object represents the HTTP response that the server sends to the client.

Common response methods include:

res.send()
res.json()
res.status()
res.redirect()

For example:

res.json({
    message: "Hello"
});

3. What is the difference between `req.params` and `req.query`?

req.params contains parameters defined in the route.

Example:

/students/10

Route:

app.get("/students/:id", ...)

Access:

req.params.id

req.query contains parameters after ?.

Example:

/students?course=Node.js

Access:

req.query.course

4. What is `req.body` in Express.js?

req.body contains data sent by the client in the request body.

For JSON requests, you normally enable:

app.use(express.json());

Then:

req.body.name

can access a name property from the JSON body.

5. What is the difference between `res.send()` and `res.json()`?

res.send() can send different types of responses, including text.

Example:

res.send("Hello World");

res.json() is designed for sending JSON responses.

Example:

res.json({
    message: "Hello World"
});

res.json() is especially common when creating APIs.

6. How do you set an HTTP status code in Express.js?

Use:

res.status()

For example:

res.status(404).json({
    message: "Student not found."
});

This sends a 404 Not Found status along with a JSON response.

7. How do you read request headers in Express.js?

You can use:

req.get("Header-Name")

For example:

const userAgent = req.get("User-Agent");

You can also access the headers object directly:

req.headers

Headers contain metadata about the HTTP request.

Written by Shubhranshu Shekhar, who has trained 20000+ students in coding.

Rishabh Kumar

Introduction

Question 1: How do you read the HTTP method from the request object?

Problem

Solution

Test

Output

Step-by-Step Explanation

Question 2: How do you read the requested URL?

Problem

Solution

Test

Output

Step-by-Step Explanation

Question 3: How do you read route parameters from the request?

Problem

Solution

Test

Output

Step-by-Step Explanation

Question 4: How do you read query parameters from the request?

Problem

Solution

Test

Output

Step-by-Step Explanation

Question 5: How do you read JSON data from the request body?

Problem

Solution

Send This JSON

Output

Step-by-Step Explanation

Question 6: How do you read request headers?

Problem

Solution

Test

Step-by-Step Explanation

Question 7: How do you send a JSON response using res.json()?

Problem

Solution

Test

Output

Step-by-Step Explanation

Another Example

Question 8: How do you send an HTTP status code with a response?

Problem

Solution

Send

Response

Step-by-Step Explanation

Common Status Codes

Question 9: How do you redirect a user using the response object?

Problem

Solution

Test

Output

Step-by-Step Explanation

Redirect to an External Website

Question 10: How do you combine request and response objects in a practical API?

Problem

Solution

Send This Request

Response

Step-by-Step Explanation

Request and Response Flow

Key Takeaways

FAQs

1. What is the req object in Express.js?

2. What is the res object in Express.js?

3. What is the difference between req.params and req.query?

4. What is req.body in Express.js?

5. What is the difference between res.send() and res.json()?

6. How do you set an HTTP status code in Express.js?

7. How do you read request headers in Express.js?

Related Posts

Question 7: How do you send a JSON response using `res.json()`?

1. What is the `req` object in Express.js?

2. What is the `res` object in Express.js?

3. What is the difference between `req.params` and `req.query`?

4. What is `req.body` in Express.js?

5. What is the difference between `res.send()` and `res.json()`?