object-orient-programming.md

Object Oriented Programming in Javascript

Object Oriented Programming a paradigm, or style of programming, that follows 4 key rules or concepts. Those are largely known as the "4 Pillars of OOP":

The Pillars of OOP:

The 4 Pillars of OOP:

1. Abstraction
2. Encapsulation
3. Inheritance
4. Polymorphism

Abstraction

Hiding of information.

Encapsulation

Grouping of information.

Inheritance

The sharing of information.

Polymorphism

Redefining of information.

Class

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

    sayHello() {
        return: `my name is ${this.name}`;
    }
}

let John = new Person("John", 110, 168);

In this example, we are creating a class of Person. It is important to denote the capital syntax of the class, this stems from older object-oriented programming languages.

Terminology

Instance

The instance is created by creating a new Class.

Methods

Methods are functions that are described within a class, and those methods then act on properties within the class.

Constructor

A constructor described the properties that exist with the object (class) and we refer to those properties of that specific instance of the class using the this keyword.

The constructor is a reserved keyword that is invoked when a class is created.

Within the contructor we typically assign the parameters defined in the class to properties of that object.

Inheritance

Using the extend keyword when initializing new classes, classes can share properties from other classes.

class Child extends ParentClass { /* initializing another constructor for Child */ }

Here we indicate that Child inherits properties from ParentClass. In this example, ParentClass is a superclass or the base class and Child is the subclass.