What is object-oriented programming?

Object-oriented programming (OOP) is a programming paradigm that is based on the concept of objects.

In OOP, an object is an instance of a class, which is a blueprint that defines the properties and methods of the object. Properties are the characteristics of the object, such as its color, size, or name. Methods are the actions that the object can perform, such as moving, rotating, or resizing.

JavaScript uses prototypes to implement OOP. Prototypes are a way of creating objects that inherit properties and methods from other objects. In JavaScript, every object has a prototype, which is another object that inherits properties and methods.

To create a new object in JavaScript, you can use the object literal notation or the constructor function notation. Here's an example of creating a new object using the object literal notation:

const car = { make: 'Toyota',

model: 'Camry',

year: 2020,

drive :function() {

console.log('Driving...');

}

};

In this example, car is an object that has the properties make, model, and year, as well as the method drive.

You can also create objects using constructor functions, which allow you to create multiple objects of the same type:

function Car(make, model, year) {

this.make = make;

this.model = model;

this.year = year;

this.drive = function() {

console.log('Driving...');

}

}

const car1 = new Car('Toyota', 'Camry', 2020);

const car2 = new Car('Honda', 'Civic', 2021);

In this example, the Car function is used as a constructor to create two new objects, car1 and car2. Each object has its own make, model, year, and drive method.

Overall, OOP in JavaScript allows you to create complex, modular applications by defining objects with their properties and methods and using inheritance to share and reuse code.

It's not enough, here is the movie so let's get deep dive into it:

1. Inheritance: Inheritance is a way to create new classes (or objects) that are a modified version of an existing class (or object). In JavaScript, inheritance is implemented using prototypes. A prototype is an object that is used as a template for creating new objects. By setting an object's prototype to another object, you can create a new object that inherits all the properties and methods of the original object. Here's an example:

// Define the parent class

class Animal {

constructor(name) {

this.name = name;

}

speak() {

console.log(`${this.name} makes a noise.`);

}

}

// Define the child class

class Dog extends Animal {

constructor(name) {

super(name);

}

speak() {

console.log(`${this.name} barks.`);

}

}

// Create a new dog object

const myDog = new Dog('Rufus');

// Call the speak method on the dog object

myDog.speak(); // Output: "Rufus barks."

In this example, the Animal class is the parent class and the Dog class is the child class that inherits from it. By using the extends keyword, we tell JavaScript that the Dog class should inherit from the Animal class. This allows the Dog class to use the name property and speak method of the Animal class, and to override the speak method with its own implementation.

1. Encapsulation: Encapsulation is the practice of hiding the internal details of an object from the outside world, and providing a public interface for interacting with the object. This is achieved in JavaScript using closures and the private keyword. Here's an example:

class Person {

constructor(name, age)

{ this.name = name;

let age = age;

this.getAge = function() { return age; }

this.setAge = function(age) {

if (age > 0 && age < 120) {

_age = age;

}

}

}

}

const person = new Person('John', 30);

console.log(person.name); // Output: "John"

console.log(person.getAge()); // Output: 30 person.setAge(40); console.log(person.getAge()); // Output: 40 person.setAge(-10);

// This won't have any effect because the age is invalid

console.log(person.getAge()); // Output: 40

In this example, the Person class has a private _age variable that is not accessible from outside the class. Instead, the class provides public getAge and setAge methods for accessing and modifying the age. This allows us to control access to the internal state of the object, and to ensure that the state is always valid.

1. Polymorphism is the ability of an object to take on many forms. In JavaScript, polymorphism can be achieved through method overriding or method overloading.

Method overriding is when a child class provides its own implementation of a method that is already defined in its parent class. The child class can then use this method to perform specific tasks based on its own needs. This allows different objects to respond differently to the same method call.

Here's an example:

class Animal {

makeSound() {

console.log('The animal makes a sound.');

}

}

class Dog extends Animal {

makeSound() {

console.log('The dog barks.');

}

}

class Cat extends Animal {

makeSound() {

console.log('The cat meows.');

}

}

const animal = new Animal();

const dog = new Dog();

const cat = new Cat();

animal.makeSound(); // Output: The animal makes a sound.

dog.makeSound(); // Output: The dog barks.

cat.makeSound(); // Output: The cat meows.

In this example, the Animal class defines a makeSound method that prints a generic message. The Dog and Cat classes override this method with their own implementations that print specific messages. When the makeSound method is called on an object of each class, it returns the appropriate message. This is an example of polymorphism through method overriding

1. Abstraction: Abstraction is the practice of hiding the implementation details of an object and exposing only the essential features to the outside world. In JavaScript, this is achieved by defining classes and objects with only the necessary properties and methods, and by using access modifiers (such as private, public, and protected) to control access to them. Here's an example:

class Car {

constructor(make, model, year)

{

this.make = make;

this.model = model;

this.year = year; }

start() {

console.log('Starting the car...');

}

drive() {

console.log('Driving the car...');

}

stop() {

console.log('Stopping the car...');

}

}

const myCar = new Car('Toyota', 'Camry', 2020);

myCar.start();

myCar.drive();

myCar.stop();

In this example, the Car class defines the essential features of a car (the make, model, year, start, drive, and stop methods) and hides the implementation details from the outside world. The myCar object can be used to start, drive, and stop the car without knowing how these methods are implemented internally. This is an example of abstraction.