# 4 principles of OOP

#### Encapsulation:

We wrap code into boxes related to one another. This box can interact with each other using the methods and properties that we make it available.

This makes the code easier to maintain and reusable.

```javascript
Ex:
const person = {
    firstName: 'Vijay',
    lastName: 'Deepak',
    getName() {
        return `${this.firstName} ${this.lastName}`;
    }
};
```

#### Abstraction:

Hiding the complexity from the user.

```javascript
Ex:
function complexFn(data) {
    // complex code & bussiness logics
}

complexFn("hi"); // code of the function is not considered
```

#### Inheritance:

Avoid code rewrite and save memory spaces with shared methods.

```javascript
Ex:
class Person {
    constructor(firstName, lastName) {
        this.firstName = firstName;
        this.lastName = lastName;
    }
    
    getFullName() {
        return `${this.firstName} ${lastName}`;
    }
}

class Men extends Person {
    constructor(firstName, lastName) {
        super(firstName, lastName);
    }
}

const vijay = new Men('Vijay', 'Deepak');
vijay.getFullName(); // Vijay Deepak

```

#### Polymorphism: ( Many Forms )

An ability to call a same method in different object, in each object responding different way. This is also known for Method overriding and Method Overloading.

**Method overriding** is the ability of the inherited class rewriting the virtual method of the base class.

**Overloading** a method (or function) is the ability for functions of the same name to be defined as long as these methods have different signatures (different set of parameters).

```javascript
Ex:
class Person {
    constructor(firstName, lastName) {
        this.firstName = firstName;
        this.lastName = lastName;
    }
    
    getFullName() {
        return `${this.firstName} ${lastName}`;
    }
}

class Men extends Person {
    constructor(firstName, lastName) {
        super(firstName, lastName);
    }
    
    getFullName() {
        return `Sorry I can't`;
    }
}

const vijay = new Men('Vijay', 'Deepak');
vijay.getFullName(); // Sorry I can't
```


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