JavaScript Object Oriented Programming Complete Note

1. JavaScript Object

An Object is a unique entity that contains properties like.

• Variable type properties
• Methods properties
• Object properties
• Array properties
• And more....

let person = {
    //Properties
    first_name: 'Jhon',
    last_name: 'Dee',
    //method
    getName:()=> {
        return (`The name of the person is ${person.first_name} ${person.last_name}`)
    }
}
console.log(person.getName());

2. Class & Object

Classes are blueprints of an Object

• A class can have many Objects because
• Class is a template while Objects are instances of the class
• Using let or var to declare variables inside a class is unnecessary because class properties are automatically scoped to the class instance and don't require explicit variable declarations

class Person {
    //Properties
    first_name='Jhon'
    last_name='Dee'
    
    //method
    getName() {
        return (`The name of the person is ${this.first_name} ${this.last_name}`)
    }
}
const person1 = new Person();
console.log(person1.getName());

3. Constructor

Class constructor is a magic method

• Constructor execute automatically when object is created
• Constructor can take parameter
• Constructor method can't return any result

class Person {
    constructor() {
        console.log('I am a constructor')
    }
}
const person1 = new Person();

class Person {
    constructor(msg) {
        console.log(msg)
    }
}
const person1 = new Person('I am a constructor');

4. Static Keyword

Class constructor is a magic method

• The static keyword is used to define a static method or property of a class.
• To call the static method we do not need to create an instance or object of the class.
• We create a static variable in JavaScript to prevent replication
• Fixed configuration, and it is also useful for caches

class Person {
    //Properties
    static first_name='Jhon'
    static last_name='Dee'
    //method
    static getName() {
        return (`The name of the person is ${this.first_name} ${this.last_name}`)
    }
}
console.log(Person.getName());

5. Inheritance

• Keyword "extends" is used to create inherit relationship between class
• For inherit relationship child class can use parent class properties

class Father {
    //Properties
     first_name='Jhon'
     last_name='Dee'
    //method
     getName() {
        return (`The name of the person is ${this.first_name} ${this.last_name}`)
    }
}

class Son extends Father{

}

const SonObj = new Son();
console.log(SonObj.getName());

6. Overriding

• Overriding works for inheritance relationship
• When child class change his parent properties , that is overriding

class Father {
    //Properties
     first_name='Jhon'
     last_name='Dee'

    //method
     getName() {
        return (`The name of the person is ${this.first_name} ${this.last_name}`)
    }
}

class Son extends Father{
    // Overriding Occurs
    first_name='Jhon Junior'
}
const SonObj = new Son();
console.log(SonObj.getName());

7. Method Overloading

• Method overloading allows you to define multiple methods with the same name but different parameter lists
• JavaScript does not natively support method overloading

8. Polymorphism

• The polymorphism is a core concept of an object-oriented paradigm that provides a way to perform a single action in different forms.
• We already know about Inheritance,Overriding,Overloading - those concepts together represent polymorphism

9. Abstraction

• Keyword "abstract" use for class abstraction
• You can't create object for abstract class
• Abstract class Always needs its inherited child class to perform
• JavaScript does not have built-in support for abstract

Thank You