Object-Oriented Programming in JavaScript

Introduction: Why Do We Need Object-Oriented Programming?

When applications grow bigger, managing code becomes difficult if everything is written in a single place. Developers need a way to organize code logically and reuse it easily.

This is where Object-Oriented Programming (OOP) comes in.

Object-Oriented Programming is a programming style that organizes code around objects and classes. Instead of writing separate pieces of code repeatedly, we create structures that represent real-world entities.

For example:

• A Car

• A Student

• A Person

Each of these can have properties (data) and behaviors (actions).

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What does Object Oriented Programming mean?

Object-Oriented Programming is a way of writing programs where we model real-world things as objects.

Each object contains:

• Properties → data about the object

• Methods → actions the object can perform

Example: A Car object

Property	Example
brand	Toyota
color	Red
speed	120

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Method	Example
start()	starts the car
stop()	stops the car

This approach makes programs more organized, reusable, and easier to maintain.

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Real Life Analogy : Blueprint -> Object

To understand OOP better, imagine building a car.

Before building a car, engineers create a blueprint (design). Using that blueprint, many cars can be produced.

Similarly in programming:

• Class → Blueprint

• Object → Actual product

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Blueprint to Object Diagram

One blueprint can create many objects.

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What is a Class in JavaScript?

A class is like a template used to create objects.

Classes define:

• What properties will an object have

• What methods the object can perform

Example:

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

Here:

• Car is the class

• It defines what a car object should contain.

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Creating Object Using Class

Objects are created using the new keyword.

Example:

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

const car1 = new Car("Toyota", "Red");
const car2 = new Car("Honda", "Black");

console.log(car1.brand);

Output:

Toyota

Here:

• car1 and car2 are objects (instances) of the class.

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Class -> Instance Relationship

A class can create multiple objects with different data.

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Constructor Method

The constructor is a special method used to initialize object properties.

It runs automatically when a new object is created.

Example:

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

const person1 = new Person("Alice", 25);

Here:

• constructor sets initial values for the object.

Real-life analogy:

Think of the constructor like filling a form when creating a new ID card.

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Methods Inside a Class

Methods are functions defined inside a class that describe actions.

Example:

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

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

const person1 = new Person("Alice", 25);
person1.greet();

Output:

Hello, my name is Alice

Methods allow objects to perform actions.

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Basics Of Encapsulation

Encapsulation means grouping data and functions together inside a class.

In simple terms:

Data + behavior = one unit

Example:

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

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

Here:

• Balance data

• Deposit function

are both inside the same class.

This keeps the code organized and secure.

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Why OOP is Useful?

Object-Oriented Programming provides many benefits:

• Code Reusability – one class can create many objects

• Better Organization – related code stays together

• Easier Maintenance – changes are easier to manage

OOP is widely used in modern JavaScript applications and frameworks.

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Assignment Practice

Step 1: Create a Student Class

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

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

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Step 2 : Creating Multiple Options

const student1 = new Student("Riya", 20);
const student2 = new Student("Arjun", 22);

student1.showDetails();
student2.showDetails();

Output:

Name: Riya, Age: 20
Name: Arjun, Age: 22

Here we created multiple student objects from one class.

Object-Oriented Programming helps developers structure programs in a logical and reusable way.

By understanding OOP, developers can write cleaner, scalable, and more maintainable code.