Object Oriented Programming in JavaScript

Introduction

As programs grow larger, managing code becomes difficult.

Instead of writing everything as separate functions and variables, developers organize code using a powerful concept called Object-Oriented Programming (OOP).

OOP allows us to structure programs around objects, making code easier to manage, reuse, and understand.

In this article we will learn:

• What Object-Oriented Programming means

• What classes are in JavaScript

• How to create objects using classes

• What constructors and methods are

• A basic idea of encapsulation

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What is Object-Oriented Programming (OOP)?

Object-Oriented Programming is a programming style where we organize code using objects and classes.

Instead of writing code like this:

let studentName = "Rahul";
let studentAge = 22;
let studentCourse = "Web Development";

We group related data together inside objects.

Example:

const student = {
  name: "Rahul",
  age: 22,
  course: "Web Development"
};

OOP takes this concept further by using classes to create objects.

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Real-World Analogy

A good way to understand OOP is using a blueprint analogy.

Think about building cars.

• A blueprint defines the design of a car.

• Many cars can be created from the same blueprint.

Real World	Programming
Car Blueprint	Class
Actual Car	Object

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What is a Class in JavaScript?

A class is a blueprint used to create objects.

Example:

class Student {

}

This class currently does nothing.

We add properties and methods to make it useful.

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Creating Objects Using Classes

Let’s create a Student class.

class Student {

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

}

Now we can create objects using this class.

const s1 = new Student("Rahul", 19);
const s2 = new Student("Amit", 21);

Each object now has its own data.

console.log(s1.name);
console.log(s2.name);

Output:

Rahul
Amit

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Constructor Method

The constructor is a special method inside a class.

It runs automatically when we create an object.

Example:

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

Explanation:

• name and age are parameters

• this.name assigns values to the object

So when we run:

new Student("Rahul", 22);

The constructor automatically sets:

name = Rahul
age = 22

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Methods Inside a Class

Classes can also contain methods.

Methods define behavior of objects.

Example:

class Student {

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

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

}

Now we can call the method.

const s1 = new Student("Rahul", 22);

s1.printDetails();

Output:

Rahul is 22 years old

Methods allow objects to perform actions.

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Encapsulation

Encapsulation means bundling data and behavior together.

In our example:

class Student {

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

  printDetails() {
    console.log(this.name, this.age);
  }

}

Here:

• Data → name, age

• Behavior → printDetails()

Both are inside the Student class.

This makes code more organized and easier to manage.

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Why OOP is Useful

Object-Oriented Programming provides several benefits.

1) Code Reusability

We can create many objects from the same class.

Example:

const s1 = new Student("Rahul", 22);
const s2 = new Student("Amit", 21);
const s3 = new Student("Priya", 23);

No need to rewrite code again.

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2) Better Code Organization

Classes keep related code together.

Example:

Student
 ├ name
 ├ age
 └ printDetails()

This structure makes programs easier to understand.

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3) Real-World Modeling

OOP allows programs to represent real-world entities.

Examples:

Real World	Programming Object
User	User class
Car	Car class
Product	Product class

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Assignment Practice

Try implementing this yourself.

Step 1: Create a Student Class

class Student {

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

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

}

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Step 2: Create Multiple Objects

const s1 = new Student("Rahul", 22);
const s2 = new Student("Amit", 21);

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Step 3: Call the Method

s1.printDetails();
s2.printDetails();

Expected Output:

Rahul is 22 years old
Amit is 21 years old

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Conclusion

Object-Oriented Programming helps organize programs using classes and objects.

In this article we learned:

• What OOP means

• Real-world blueprint analogy

• What classes are in JavaScript

• How to create objects using classes

• Constructor methods

• Methods inside a class

• Basic idea of encapsulation

These concepts make JavaScript programs more structured, reusable, and easier to maintain.