Understanding Object-Oriented Programming in JavaScript

Object-Oriented Programming (OOP) is a way of writing code where we organize data and behavior into objects. It helps developers build programs that are structured, reusable, and easier to maintain.

JavaScript supports Object-Oriented Programming through classes and objects, allowing us to model real-world entities in our code.

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What Object-Oriented Programming (OOP) Means

Object-Oriented Programming is a programming approach where we create objects that contain both data and functions.

• Data → stored as properties

• Functions → stored as methods

Instead of writing many separate variables and functions, OOP lets us group related information together inside objects.

Real-World Analogy: Blueprint → Objects

A simple way to understand OOP is by using the idea of a blueprint.

Imagine a car factory.

• The blueprint describes how a car should look and behave.

• Many cars can be created from the same blueprint.

In programming:

• Class → blueprint

• Object → actual item created from the blueprint

Example:

Blueprint: Car
Objects: Car1, Car2, Car3

Each car has the same structure but can have different values.

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What is a Class in JavaScript?

A class is a blueprint used to create objects.

It defines what properties and methods an object will have.

Example:

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

Here, the class Car describes the structure for creating car objects.

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Creating Objects Using Classes

Objects are created using the new keyword.

Example:

const car1 = new Car("Toyota", 2022);
const car2 = new Car("Honda", 2021);

Now we have two objects created from the same class.

car1 → Toyota, 2022
car2 → Honda, 2021

This shows how classes allow us to reuse the same structure to create multiple objects.

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The Constructor Method

The constructor is a special method inside a class.

It runs automatically when a new object is created and is used to initialize object properties.

Example:

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

const person1 = new Person("Rahul", 21);

Here:

• name and age are assigned when the object is created.

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Methods Inside a Class

Classes can also contain methods, which define the actions objects can perform.

Example:

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

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

const user = new Person("Rahul", 21);
user.greet();

Output:

Hello, my name is Rahul

Here, greet is a method that belongs to the Person class.

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Basic Idea of Encapsulation

Encapsulation means keeping data and the functions that operate on that data together inside a class.

Instead of managing many separate variables and functions, we store everything inside one structure.

Example:

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

  start() {
    console.log(this.brand + " car started");
  }
}

The data (brand) and behavior (start) are bundled together, which makes the code easier to organize.

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Why OOP is Useful

Object-Oriented Programming helps in:

• Code reusability – use the same class to create many objects

• Better organization – group related data and methods

• Easier maintenance – structured code is easier to update

• Modeling real-world entities

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Practice Assignment

Try creating your own class to practice OOP concepts.

Task

1. Create a class called Student

2. Add properties name and age

3. Add a method that prints the student's details

4. Create multiple student objects

Example Solution

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

  printDetails() {
    console.log(this.name + " is " + this.age + " years old.");
  }
}

const student1 = new Student("Aman", 20);
const student2 = new Student("Neha", 22);

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

Output:

Aman is 20 years old.
Neha is 22 years old.

This example shows how one class can be used to create multiple objects with different data.