Object-Oriented Programming (OOP) in JavaScript

Object-Oriented Programming (OOP) is a programming approach where code is structured using objects and classes. It helps in writing modular, reusable, and maintainable code.

The four main principles of OOP are:

Encapsulation
Inheritance
Polymorphism
Abstraction

1. Encapsulation

Encapsulation is the concept of hiding data and controlling access through methods.

class BankAccount {
  #balance;

  constructor(owner, balance) {
    this.owner = owner;
    this.#balance = balance;
  }

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

  getBalance() {
    return this.#balance;
  }
}

const acc = new BankAccount("Rahul", 1000);
acc.deposit(500);

console.log(acc.getBalance());

2. Inheritance (Using super)

Inheritance allows one class to reuse properties and methods of another class.

class Animal {
  constructor(name) {
    this.name = name;
  }

  speak() {
    console.log(this.name + " makes a sound");
  }
}

class Dog extends Animal {
  constructor(name, breed) {
    super(name); // calling parent constructor
    this.breed = breed;
  }

  bark() {
    console.log(this.name + " barks");
  }
}

const dog = new Dog("Tommy", "Labrador");

dog.speak();
dog.bark();

3. Polymorphism

Polymorphism means the same method behaves differently for different objects.

class Animal {
  speak() {
    console.log("Animal makes sound");
  }
}

class Dog extends Animal {
  speak() {
    console.log("Dog barks");
  }
}

class Cat extends Animal {
  speak() {
    console.log("Cat meows");
  }
}

const d = new Dog();
const c = new Cat();

d.speak();
c.speak();

4. Abstraction

Abstraction hides internal implementation and exposes only essential functionality.

class Car {
  start() {
    this.#checkEngine();
    console.log("Car started");
  }

  #checkEngine() {
    console.log("Checking engine...");
  }
}

const car = new Car();
car.start();

Static Methods

Static methods belong to the class itself, not to instances.

class MathHelper {
  static add(a, b) {
    return a + b;
  }
}

console.log(MathHelper.add(5, 3));

Conclusion

OOP in JavaScript helps you write clean, structured, and reusable code by organizing logic into classes and objects.

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