Introduction: The Reception Desk of AQAD

Imagine AQAD has grown into a large B2B marketplace.

Every day:

Vendors upload products
Retailers place orders
Logistic partners update deliveries
Employees monitor operations

Now imagine there is no reception desk.

Customers arrive.

Nobody receives them.

Nobody understands their requests.

Nobody provides responses.

Chaos.

A backend server works very much like a reception desk.

It receives requests.

Processes them.

Returns responses.

This communication happens through something called:

HTTP

Before Node.js can become a real backend application, it must be able to:

Accept requests
Process requests
Send responses

This chapter teaches exactly how that happens.

By the end of this chapter, you will understand how APIs and backend systems actually begin.

Node.js HTTP Module, APIs, Interview Questions & Project Structure Explained

What Is HTTP?

HTTP stands for:

HyperText Transfer Protocol

Don't worry about memorizing the full form.

Think of HTTP as a language.

A language used by:

Browser
    ↔
Server

to communicate.

Real-Life Analogy

Imagine a customer enters a restaurant.

Customer:

Can I have a coffee?

Waiter:

Sure.

Kitchen prepares coffee.

Waiter returns:

Here is your coffee.

The conversation contains:

Request

Customer asking for something.

Response

Restaurant providing something.

HTTP works exactly the same way.

Understanding Client and Server

Every HTTP communication involves two parties.

Client

Requests information.

Examples:

Browser
Mobile App
React Application
React Native Application

Server

Provides information.

Examples:

Node.js Backend
Express API
AQAD Backend

Example:

Retailer App
      ↓
Request Products
      ↓
AQAD Backend
      ↓
Return Products

What Happens When You Open a Website?

Suppose you visit:

https://aqad.com

Browser sends:

HTTP Request

Server processes it.

Server returns:

HTTP Response

Browser displays result.

This happens in milliseconds.

Creating Your First HTTP Server

Node.js includes a built-in module:

http

Import it:

const http = require('http');

No installation required.

Creating the Server

Example:

const http = require('http');

const server = http.createServer();

server.listen(3000);

Server now listens on:

http://localhost:3000

But it doesn't do anything yet.

Understanding createServer()

Think of:

http.createServer()

as opening the reception desk.

The desk exists.

But nobody is handling customers yet.

Handling Requests

Let's improve our server.

const http = require('http');

const server =
http.createServer(
    (req, res) => {

        res.end(
            'Welcome to AQAD'
        );

    }
);

server.listen(3000);

Visit:

http://localhost:3000

Output:

Welcome to AQAD

Congratulations.

You built your first backend server.

Understanding req and res

Inside:

(req, res)

Node.js provides two objects.

req

Request Object.

Contains information sent by client.

res

Response Object.

Used to send information back.

Think of:

req  as: Customer Request

and

res  as: Restaurant Response

Understanding listen()

Example:

server.listen(3000);

Meaning:

Server

Listen on Port 3000

What Is a Port?

Think of a building.

One building.

Many doors.

Door 3000

Door 5000

Door 8080

Ports help computers identify services.

Common ports:

Port	Purpose
80	HTTP
443	HTTPS
3000	Development
5000	APIs
3306	MySQL

Adding a Startup Message

Useful for development.

server.listen(3000,() => {

             console.log( 'Server Running');

                   }
                 );

Output:

Server Running

Accessing Request Information

Suppose user visits:

http://localhost:3000

Print request URL.

const server =
http.createServer(
    (req, res) => {

        console.log(
            req.url
        );

        res.end('Hello');

    }
);

Output:

Visit:

http://localhost:3000/products

Output:

/products

Interesting.

Now the server knows what page was requested.

Understanding Routing

Routing means:

Different URL
      ↓
Different Response

Example:

const server = http.createServer((req, res) => {

                      if(req.url === '/'){

            res.end('Home Page');

                     }

           }
        );

Visit:

Output:

Home Page

Multiple Routes

Example:

const server =  http.createServer((req, res) => {

                         if(req.url === '/'){

                        res.end('Home'); }

                 else if(req.url === '/products'){

             res.end('Products');

         }else{

         res.end('Page Not Found' ); }

     });

Visit:

/products

Output:

Products

AQAD Example

Imagine:

/products

/orders

/vendors

Each route returns different information.

Example:

if(req.url === '/products'){

    res.end('Product List');
}

Understanding HTTP Methods

URL alone is not enough.

Clients also send methods.

Common methods:

Method	Purpose
GET	Fetch data
POST	Create data
PUT	Update data
DELETE	Remove data

GET Request

Retrieve information.

Example:

GET /products

Meaning:

Give me products.

POST Request

Create information.

Example:

POST /products

Meaning:

Create product.

Checking Request Method

Example:

console.log(req.method);

Output:

GET

AQAD Example

Retailer:

GET /products

Fetch products.

Vendor:

POST /products

Create product.

Returning HTML

Response can contain HTML.

Example:

res.end(`<h1>AQAD Marketplace</h1>`);

Browser displays:

AQAD Marketplace

as heading.

Returning JSON

Modern APIs mostly return JSON.

Example:

const products = [
    {
        id: 1,
        name: 'Rice'
    }
];

res.end(
JSON.stringify(products)
);

Output:

[
  {
    "id":1,
    "name":"Rice"
  }
]

Why JSON Is Important

Frontend applications understand JSON easily.

Examples:

React
React Native
Angular
Vue

All communicate using JSON.

Setting Response Headers

Headers provide metadata.

Example:

res.setHeader(
'Content-Type',
'application/json'
);

Then:

res.end(
JSON.stringify(data)
);

Browser now understands:

JSON Response

Understanding Status Codes

Every response includes a status.

Examples:

Code	Meaning
200	Success
201	Created
400	Bad Request
401	Unauthorized
404	Not Found
500	Server Error

Example

res.statusCode = 200;

res.end(
'Success'
);

Not Found Example

res.statusCode = 404;

res.end('Page Not Found');

Output:

AQAD API Example

if(req.url === '/products'){

res.statusCode = 200;
res.end('Products Found');

}

Unknown route:

res.statusCode = 404;

res.end('Not Found');

Building a Mini AQAD API

Example:

const http = require('http');

const server = http.createServer((req,res)=>{

               if(req.url === '/products'){
                const products = [
                                   {
                                   id:1,
                                   name:'Rice'},
                                  {
                                  id:2,
                                 name:'Milk'}
                                              ];

res.setHeader('Content-Type','application/json');

res.end(JSON.stringify(products));

                       }else{
                   res.statusCode = 404;
               res.end('Route Not Found');  }
                                                  });
              server.listen(3000);

Visit:

http://localhost:3000/products

Output:

[
 {
  "id":1,
  "name":"Rice"
 },
 {
  "id":2,
  "name":"Milk"
 }
]

Common Beginner Mistakes

Mistake 1

Forgetting res.end()

Bad:

res.write('Hello');

Without: res.end();

request never finishes.

Mistake 2

Ignoring Status Codes

Always return meaningful status codes.

Mistake 3

Sending Objects Directly

Bad:

res.end(products);

Good:

res.end(JSON.stringify(products));

Mistake 4

Not Setting Content-Type

JSON responses should use:

application/json

Mini Exercises

Exercise 1

Create:

route.

Return:

Welcome

Exercise 2

Create:

/products

route.

Return JSON.

Exercise 3

Print:

req.url

for every request.

Exercise 4

Return:

404 Not Found

for unknown routes.

Try It Yourself

Create:

const http =
require('http');

const server = http.createServer((req,res)=>{
                   
                     res.statusCode = 200;

            res.end('Hello AQAD');

               });

server.listen(3000,()=>{

         console.log('Server Running');

                 });

Run:

node app.js

Visit:

http://localhost:3000

Observe your first real backend response.

Interview Question

What is the difference between req and res in Node.js?

Good Answer:

The req object contains information sent by the client such as URL, method, and headers. The res object is used by the server to send responses back to the client including data, headers, and status codes.

Real Developer Insight

When beginners first create:

http.createServer()

it may look simple.

But behind this small function lies the foundation of:

REST APIs
Express.js
Authentication systems
Payment gateways
E-commerce platforms
Social media applications

Everything starts with understanding how a server receives requests and sends responses.

Once you understand HTTP servers, frameworks like Express become much easier because they are built on top of the same concepts.

Node.js Interview Questions and Real-World Scenarios

Introduction: Why Interview Preparation Matters

Imagine two developers applying for the same Node.js Backend Developer position.

Both have learned:

JavaScript
Node.js
APIs
Databases

Both can write code.

Both understand the basics.

But during the interview:

Developer A memorizes definitions.

Developer B explains:

Why Node.js was created
How the Event Loop works
Why Streams improve performance
How a production backend handles thousands of users

Which developer gets hired?

Usually Developer B.

Because companies don't hire developers who simply memorize answers.

They hire developers who understand how systems work.

The goal of this chapter is not to help you memorize interview answers.

The goal is to help you think like a backend developer.

We'll cover:

Beginner questions
Intermediate questions
Advanced scenarios
Real production examples
AQAD marketplace case studies

Beginner-Level Questions

Question 1: What Is Node.js?

Answer:

Node.js is a JavaScript runtime environment built on Google's V8 Engine.

It allows JavaScript to run outside the browser and enables developers to build backend applications, APIs, command-line tools, and real-time systems.

Interview Tip

Don't say:

"Node.js is a programming language."

That is incorrect.

JavaScript is the language.

Node.js is the runtime.

Question 2: Why Was Node.js Created?

Answer:

Before Node.js, JavaScript mainly ran inside browsers.

Ryan Dahl created Node.js to allow JavaScript to run on servers and handle many concurrent connections efficiently using an event-driven, non-blocking architecture.

Question 3: What Is the V8 Engine?

Answer:

V8 is Google's JavaScript engine.

It converts JavaScript code into machine code so the computer can execute it quickly.

Node.js uses V8 to run JavaScript outside the browser.

Question 4: What Is NPM?

Answer:

NPM stands for Node Package Manager.

It helps developers install, manage, and share reusable packages.

It includes:

Package registry
Package manager
CLI tool

Question 5: What Is package.json?

Answer:

package.json is the configuration file of a Node.js project.

It contains:

Project information
Dependencies
Scripts
Version details
Metadata

Intermediate-Level Questions

Question 6: What Is the Event Loop?

Answer:

The Event Loop is the mechanism that allows Node.js to handle asynchronous operations without creating a new thread for every request.

It continuously checks:

Call Stack

Callback Queue

Microtask Queue

and decides what should execute next.

Restaurant Analogy

Think of the Event Loop as a head waiter.

The waiter doesn't cook food.

The waiter coordinates activities and ensures tasks happen at the right time.

Question 7: What Is Non-Blocking I/O?

Answer:

Non-blocking I/O allows Node.js to start an operation and continue doing other work instead of waiting for the operation to finish.

Example:

fs.readFile(
    'data.txt',
    callback
);

Node.js continues executing other code while the file is being read.

Question 8: What Is libuv?

Answer:

libuv is a C library used by Node.js.

It provides:

Event Loop implementation
Thread Pool
Non-blocking I/O operations

libuv helps Node.js perform tasks such as:

File operations
DNS lookups
Networking

Question 9: Difference Between require() and import?

require()

CommonJS

const fs =
require('fs');

import

ES Modules

import fs
from 'fs';

Modern projects increasingly use:

import
export

Question 10: What Are Environment Variables?

Answer:

Environment variables store configuration values outside the codebase.

Examples:

PORT

JWT_SECRET

DATABASE_URL

AWS_REGION

They improve:

Security
Flexibility
Deployment management

Event Loop Interview Questions

These questions appear frequently.

Question 11: Predict the Output

console.log('A');

setTimeout(() => {
    console.log('B');
}, 0);

console.log('C');

Output:

A
C
B

Why?

The timeout callback enters the callback queue.

Node.js executes synchronous code first.

Question 12: Predict the Output

console.log('Start');

Promise.resolve()
.then(() => {
    console.log('Promise');
});

console.log('End');

Output:

Start
End
Promise

Why?

Promises use:

Microtask Queue

which executes after synchronous code finishes.

Streams Interview Question

Question 13: Why Use Streams?

Answer:

Streams process data in chunks instead of loading entire files into memory.

Benefits:

Lower memory consumption
Better performance
Improved scalability

Example

Bad:

fs.readFile()

for huge files.

Better:

fs.createReadStream()

Buffers Interview Question

Question 14: What Is a Buffer?

Answer:

A Buffer is a temporary memory area used to store raw binary data.

It is commonly used for:

Files
Streams
Images
Network communication

Modules Interview Question

Question 15: What Is Module Caching?

Answer:

When a module is loaded using:

require()

Node.js stores it in memory.

Future requests use the cached version instead of reading the file again.

Benefits:

Faster execution
Better performance

Advanced Interview Questions

Question 16: Why Is Node.js Single-Threaded?

Answer:

Node.js uses a single-threaded event loop to simplify concurrency and reduce resource consumption.

However, Node.js is not limited to one thread.

libuv internally uses:

Thread Pool

for tasks like:

File operations
DNS lookups
Cryptography

Question 17: Can Node.js Handle Thousands of Users?

Answer:

Yes.

Because Node.js uses:

Event-driven architecture
Non-blocking I/O
Efficient resource utilization

it can handle many concurrent connections.

Example

Netflix and other large-scale companies have used Node.js for high-traffic systems.

Question 18: Difference Between process.nextTick() and setTimeout()

process.nextTick()

Runs before the next Event Loop phase.

setTimeout()

Runs during the Timers phase.

Example:

process.nextTick(() => {
    console.log('Tick');
});

setTimeout(() => {
    console.log('Timeout');
}, 0);

Output:

Tick
Timeout

Real Production Scenarios

These questions test practical thinking.

Scenario 1

AQAD API Suddenly Becomes Slow

Symptoms:

High Response Time

Users Complaining

CPU Usage Increased

What Would You Check?

Answer:

CPU usage
Memory usage
Database performance
Slow queries
Application logs
Network latency

Tools:

CloudWatch
PM2
Grafana
Node.js logs

Scenario 2

Memory Usage Keeps Increasing

Symptoms:

Application Starts Fine

Memory Grows Constantly

Eventually Crashes

Likely Cause:

Memory Leak

What To Investigate?

Global variables
Unclosed connections
Cached data
Event listeners

Scenario 3

Large CSV Upload Crashes Server

Vendor uploads:

5 GB CSV

Server crashes.

Bad Solution:

fs.readFile()

Better Solution:

fs.createReadStream()

Use streams.

AQAD Marketplace Case Study

Let's combine everything.

Requirement

Retailer places order.

System must:

Save Order

Update Inventory

Notify Vendor

Send Email

Generate Analytics

Beginner Solution

saveOrder();

updateInventory();

sendEmail();

notifyVendor();

analytics();

Everything tightly coupled.

Better Solution

orderEmitter.emit(
    'orderCreated'
);

Listeners:

Inventory Service

Notification Service

Analytics Service

Email Service

More scalable.

System Design Style Question

How Would You Design Product Upload API?

Answer:

Step 1

Authentication

JWT verification.

Step 2

Validate request.

Step 3

Upload images.

Step 4

Store files.

S3 or file storage.

Step 5

Save product metadata.

Database.

Step 6

Emit event.

productCreated

Step 7

Update analytics.

Frequently Asked Node.js Interview Mistakes

Mistake 1

Saying:

Node.js is a programming language.

Wrong.

Mistake 2

Thinking:

setTimeout(fn, 0)

runs immediately.

Wrong.

Mistake 3

Not understanding Event Loop.

Very common interview failure.

Mistake 4

Confusing Node.js with Express.js.

Express is a framework.

Node.js is the runtime.

Mistake 5

Ignoring real-world architecture questions.

Senior interviews focus on:

Scalability
Reliability
Monitoring
Security

not just syntax.

Mini Interview Challenge

Explain in your own words:

Question 1

Why is Node.js suitable for APIs?

Question 2

Why are streams useful?

Question 3

What happens when:

node app.js

is executed?

Question 4

How does Event Loop improve scalability?

Real Developer Advice

Many developers spend weeks memorizing interview answers.

Unfortunately:

Interviewers can easily detect memorization.

Instead:

Focus on understanding:

Why Node.js exists
How requests flow
How Event Loop works
How data moves through streams
How backend systems scale

When you understand the concepts, answers become natural.

Real Backend Project Structure – How Professional Node.js Applications Are Organized

Introduction: Why Professional Projects Don't Have Everything Inside app.js

When developers first learn Node.js, their projects usually look like this:

project
│
└── app.js

Inside:

// Login Logic

// Product Logic

// Orders Logic

// Payment Logic

// Email Logic

// Database Logic

// Validation Logic

// File Upload Logic

At first this feels manageable.

Then the project grows.

After a few weeks:

app.js
=
2,000 Lines

A few months later:

app.js
=
10,000 Lines

Now imagine AQAD running like this.

One employee handles:

Vendor onboarding
Retailer onboarding
Orders
Inventory
Payments
Logistics
Analytics

Impossible.

Businesses grow by creating departments.

Software grows exactly the same way.

Professional backend applications divide responsibilities into folders and modules.

This chapter shows how real Node.js applications are structured in production environments.

The Goal of Project Structure

A good backend structure helps:

Scalability

Add new features easily.

Maintainability

Fix bugs faster.

Team Collaboration

Multiple developers work simultaneously.

Code Reusability

Avoid duplicate logic.

Clean Architecture

Easy to understand.

AQAD Backend Structure

A professional Node.js project might look like:

aqad-backend
│
├── src
│
├── config
│
├── routes
│
├── controllers
│
├── services
│
├── middlewares
│
├── models
│
├── validations
│
├── utils
│
├── uploads
│
├── logs
│
├── app.js
│
└── server.js

Don't worry.

We'll understand every folder.

Understanding Request Flow

Before discussing folders, let's understand what happens when a request arrives.

Example:

Retailer
    ↓
GET /products
    ↓
Route
    ↓
Middleware
    ↓
Controller
    ↓
Service
    ↓
Database
    ↓
Response

This flow exists in most professional backend systems.

Routes Folder

Think of routes as reception desks.

Real-Life Analogy

A customer enters AQAD headquarters.

Reception asks:

Which department do you need?

Routes perform the same job.

Example:

routes
│
├── userRoutes.js
├── productRoutes.js
├── orderRoutes.js
└── paymentRoutes.js

Example:

router.get(
    '/products',
    getProducts
);

The route simply decides:

This request belongs to Product Controller

Nothing more.

Controllers Folder

Controllers handle incoming requests.

Restaurant Analogy

Customer says:

I want a coffee.

Waiter receives the request.

The waiter doesn't prepare the coffee.

The waiter forwards the request.

Controllers work similarly.

Example:

controllers
│
├── userController.js
├── productController.js
└── orderController.js

Example:

const getProducts =
async (req, res) => {

    const products =
    await productService
    .getProducts();

    res.json(products);

};

Controller responsibilities:

Receive request
Validate input
Call service
Send response

Why Controllers Should Stay Small

Bad:

const getProducts =
async (req,res)=>{

// 500 lines
// Database
// Validation
// Business Logic

}

Good:

const getProducts =
async (req,res)=>{

const products =
await productService
.getProducts();

res.json(products);

}

Controllers should remain lightweight.

Services Folder

Services contain business logic.

This is where the real work happens.

AQAD Example

When retailer places order:

Business rules may include:

Check Inventory

Calculate Total

Apply Discounts

Calculate Tax

Generate Invoice

Create Order

These belong inside services.

Example:

services
│
├── productService.js
├── orderService.js
└── paymentService.js

Example:

const createOrder =
async (data) => {

    // Inventory Check

    // Pricing Logic

    // Order Creation

};

Why Services Matter

Without services:

Controllers become massive.

With services:

Controller
     ↓
Service
     ↓
Database

Clean separation.

Models Folder

Models represent database structures.

AQAD Example

Tables:

Users

Products

Orders

Payments

Each table gets a model.

Example:

models
│
├── userModel.js
├── productModel.js
└── orderModel.js

Model responsibility:

Interact with database.

Example:

const getProductById =
async (id) => {

    return productTable
    .find(id);

};

Validation Folder

Validation protects applications from bad data.

Example

Vendor creates product.

Bad request:

{
  "price": -100
}

Should not be accepted.

Validation checks:

Required Fields

Email Format

Phone Format

Password Rules

Price Rules

Folder:

validations
│
├── userValidation.js
├── productValidation.js
└── orderValidation.js

Example:

const schema = {

    title: required,

    price: positive

};

Middleware Folder

Middleware sits between:

Request
     ↓
Controller

Think of middleware as security guards.

Authentication Middleware

Example:

User Request
      ↓
JWT Verification
      ↓
Allow Access

Example:

const authMiddleware =
(req,res,next)=>{

// Verify Token

next();

}

Logging Middleware

Every request gets recorded.

Example:

GET /products

POST /orders

PUT /users

Useful for monitoring.

Rate Limiting Middleware

Protects APIs.

Example:

100 Requests
Per Minute

Prevent abuse.

Config Folder

Stores application configuration.

Example:

config
│
├── database.js
├── aws.js
└── environment.js

Instead of:

const region =
'me-central-1';

hardcoded everywhere.

Use:

config.aws.region

Environment Variables

Never store secrets inside code.

Bad:

const secret =
'my-secret-key';

Good:

process.env.JWT_SECRET

Example:

PORT=5000

JWT_SECRET=secret

AWS_REGION=me-central-1

Utils Folder

Utilities contain reusable helper functions.

Example:

utils
│
├── dateHelper.js
├── fileHelper.js
└── generateId.js

Example:

generateOrderId()

used throughout project.

Uploads Folder

Stores uploaded files.

AQAD Example:

uploads
│
├── products
│
├── vendors
│
└── retailer-documents

Contains:

Images
PDFs
Trade licenses
Documents

Logs Folder

Stores application logs.

Example:

logs
│
├── errors.log
├── orders.log
└── system.log

Useful for troubleshooting.

app.js vs server.js

Many professional projects separate them.

app.js

Contains:

Routes

Middlewares

Configurations

Example:

const app =
express();

app.use(...);

server.js

Starts server.

Example:

app.listen(
5000
);

This separation improves testing.

Real AQAD Request Flow

Retailer requests:

GET /products

Flow:

Route
   ↓
Auth Middleware
   ↓
Controller
   ↓
Service
   ↓
Database
   ↓
Response

Let's see this visually.

Route

router.get(
'/products',
getProducts
);

Controller

const getProducts =
async(req,res)=>{

const data =
await productService
.getProducts();

res.json(data);

}

Service

const getProducts =
async()=>{

return productModel
.getAll();

}

Model

const getAll =
async()=>{

return db.products;

}

Response:

[
 {
  "id":1,
  "title":"Rice"
 }
]

Each layer has one responsibility.

Why This Architecture Scales

Imagine AQAD grows from:

1,000 Retailers

to:

100,000 Retailers

New features become easier because:

Routes stay organized
Controllers stay clean
Services contain logic
Models manage data

The project remains maintainable.

Common Beginner Mistakes

Mistake 1

Putting Everything Inside Controller

Bad:

// Validation

// Database

// Business Logic

// Response

inside controller.

Mistake 2

Skipping Services

Many beginners directly call database from controller.

This becomes difficult to maintain.

Mistake 3

Hardcoding Secrets

Bad:

const jwtSecret =
'123456';

Always use environment variables.

Mistake 4

Creating Huge Utility Files

Bad:

utils.js

containing:

300 Functions

Split logically.

Mistake 5

Ignoring Logging

Production systems need logs.

Mini Exercise

Design folder structure for:

Library Management System

Create:

routes

controllers

services

models

middlewares

and decide responsibilities.

Try It Yourself

Create:

project
│
├── routes
├── controllers
├── services
├── models
│
├── app.js
└── server.js

Build:

GET /products

flow using all layers.

This exercise helps understand architecture much better than memorizing theory.

Real Developer Insight

Junior developers often think:

"A good developer writes code."

Senior developers know:

"A good developer organizes code."

Most production issues are not caused by lack of coding ability.

They are caused by poor architecture.

A clean architecture allows:

Faster development
Easier debugging
Better teamwork
Easier scaling

This is why companies care so much about project structure.

Node.js HTTP Module, APIs, Interview Questions & Project Structure Explained

Introduction: The Reception Desk of AQAD

What Is HTTP?

Real-Life Analogy

Request

Response

Understanding Client and Server

Client

Server

What Happens When You Open a Website?

Creating Your First HTTP Server

Creating the Server

Understanding createServer()

Handling Requests

Understanding req and res

req

res

Understanding listen()

What Is a Port?

Adding a Startup Message

Accessing Request Information

Understanding Routing

Multiple Routes

AQAD Example

Understanding HTTP Methods

GET Request

POST Request

Checking Request Method

AQAD Example

Returning HTML

Returning JSON

Why JSON Is Important

Setting Response Headers

Understanding Status Codes

Example

Not Found Example

AQAD API Example

Building a Mini AQAD API

Common Beginner Mistakes

Mistake 1

Mistake 2

Mistake 3

Mistake 4

Mini Exercises

Exercise 1

Exercise 2

Exercise 3

Exercise 4

Try It Yourself

Interview Question

What is the difference between req and res in Node.js?

Real Developer Insight

Node.js Interview Questions and Real-World Scenarios

Introduction: Why Interview Preparation Matters

Beginner-Level Questions

Question 1: What Is Node.js?

Interview Tip

Question 2: Why Was Node.js Created?

Question 3: What Is the V8 Engine?

Question 4: What Is NPM?

Question 5: What Is package.json?

Intermediate-Level Questions

Question 6: What Is the Event Loop?

Restaurant Analogy

Question 7: What Is Non-Blocking I/O?

Question 8: What Is libuv?

Question 9: Difference Between require() and import?

require()

import

Question 10: What Are Environment Variables?

Event Loop Interview Questions

Question 11: Predict the Output

Why?

Question 12: Predict the Output

Why?

Streams Interview Question

Question 13: Why Use Streams?

Example

Buffers Interview Question

Question 14: What Is a Buffer?