Modern applications in JavaScript often deal with complex data and behaviors.
To organize code better, developers use a programming style called Object-Oriented Programming (OOP).

OOP helps us structure programs using objects and classes, making code easier to manage, reuse, and understand.

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What is Object-Oriented Programming (OOP)?

Object-Oriented Programming is a programming approach where we organize code into objects that contain data and functions.

In simple words:

• Objects store information

• Methods perform actions on that information

Example:

A student object might have:

• name

• age

• course

And a method like:

• displayStudentDetails()

This approach helps keep related data and behavior together.

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Real-World Analogy: Blueprint → Objects

Think about building cars.

A blueprint describes how a car should look and behave:

• color

• engine

• speed

• start()

From that blueprint, we can create many cars.

In programming:

Real World	Programming
Blueprint	Class
Actual Car	Object
Features	Properties
Actions	Methods

So a class acts as a blueprint, and objects are created from that blueprint.

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What is a Class in JavaScript?

A class is a template used to create objects.

Classes were introduced in modern JavaScript through ES6.

Example class:

class Person {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }
}

Here:

• Person is the class

• name and age are properties

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Creating Objects Using Classes

Objects are created using the new keyword.

Example:

class Person {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }
}

let person1 = new Person("Rahul", 25);
let person2 = new Person("Amit", 30);

console.log(person1.name);

Output:

Rahul

Each object has its own data.

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Constructor Method

The constructor is a special method inside a class.

It runs automatically when an object is created.

Example:

class Car {
  constructor(brand, year) {
    this.brand = brand;
    this.year = year;
  }
}

When we create an object:

let myCar = new Car("Toyota", 2022);

The constructor automatically assigns:

brand = Toyota
year = 2022

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Methods Inside a Class

Classes can also contain methods (functions inside the class).

Example:

class Person {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }

  greet() {
    console.log("Hello, my name is " + this.name);
  }
}

Using the method:

let user = new Person("Ravi", 22);

user.greet();

Output:

Hello, my name is Ravi

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Basic Idea of Encapsulation

Encapsulation means keeping related data and methods together inside a class.

Example:

class BankAccount {
  constructor(balance) {
    this.balance = balance;
  }

  deposit(amount) {
    this.balance += amount;
  }
}

Here:

• balance is stored inside the object

• deposit() modifies it

So data and behavior stay together.

This makes code organized and easier to maintain.

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Assignment Practice

Create a Student Class

class Student {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }

  printDetails() {
    console.log("Name: " + this.name);
    console.log("Age: " + this.age);
  }
}

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Create Multiple Student Objects

let student1 = new Student("Rahul", 20);
let student2 = new Student("Priya", 21);

student1.printDetails();
student2.printDetails();

Output:

Name: Rahul
Age: 20

Name: Priya
Age: 21

Each student object has its own properties but shares the same class structure.

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Visual Representation

Class → Objects

Student (Class)
│
├── student1 → Rahul, 20
└── student2 → Priya, 21

The class defines the structure, while objects store actual values.

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Why OOP is Important

Object-Oriented Programming helps developers:

• Organize large programs

• Reuse code easily

• Model real-world systems

• Keep code clean and maintainable

You will see OOP concepts used heavily in frameworks like React, backend development, and large-scale applications.