Understanding Object-Oriented Programming in JavaScript

What Object-Oriented Programming (OOP) Means

Object-Oriented Programming (OOP) is a programming approach where we organize code using objects and classes.
Instead of writing separate code again and again, we create reusable structures that represent real-world entities.

In OOP, objects contain data (properties) and behavior (methods).

This makes programs:

• Easier to understand

• Easier to maintain

• More reusable

JavaScript supports OOP concepts using classes and objects.

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Real-World Analogy (Blueprint → Objects)

To understand OOP better, imagine a car blueprint.

A blueprint defines how a car should be built:

• color

• model

• speed

Using this blueprint, we can create many cars.

Similarly in programming:

• Class → Blueprint

• Object → Real instance created from blueprint

Example:

Car Blueprint → Car1, Car2, Car3

All cars are created from the same blueprint but they can have different values.

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What is a Class in JavaScript

A class is like a template or blueprint used to create objects.

It defines:

• properties (data)

• methods (functions)

In JavaScript, classes were introduced in ES6 to make OOP easier to write and understand.

Basic syntax:

class Person {
}

This class does not yet contain properties or methods, but it acts as a structure for creating objects.

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Creating Objects Using Classes

Once a class is created, we can create objects from it using the new keyword.

Example:

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

const person1 = new Person("Rahul", 20);
const person2 = new Person("Aman", 22);

Here:

• Person is the class

• person1 and person2 are objects created from the class

Each object has its own data.

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Constructor Method

A constructor is a special method that runs automatically when a new object is created.

It is mainly used to initialize object properties.

Example:

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

Here:

• name and age are parameters

• this.name and this.age store the values inside the object

So whenever we create a new object, the constructor assigns the values.

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Methods Inside a Class

Methods are functions defined inside a class that describe the behavior of objects.

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("Rahul", 20);
person1.greet();

Output:

Hello, my name is Rahul

Methods allow objects to perform actions.

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Basic Idea of Encapsulation

Encapsulation means keeping data and methods together inside a class and controlling access to them.

This helps:

• protect data

• organize code better

Example:

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

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

Here the balance and deposit behavior are wrapped inside the same class.

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Assignment Example: Student Class

Let’s create a Student class as an example.

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

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

const student1 = new Student("Rohan", 20);
const student2 = new Student("Anjali", 21);

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

Output:

Name: Rohan, Age: 20
Name: Anjali, Age: 21

Here we created multiple student objects from the same class.

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Why OOP is Useful

Object-Oriented Programming helps in:

• Code reusability

• Better organization of code

• Easier maintenance

• Modeling real-world entities in programs

Because of these advantages, OOP is widely used in modern software development.