An intro to OOP in Javascript

oop.js

// a simple object literal
var person = {
	name: 'Alex',
	hi: function() {
		alert("Hi! I'm " + this.name + " .");
	}
}

// check the properties and methods
person.name;
person.hi();

// this object is an instance of the Object type
person instanceof Object;


// another way to create an object
var person = new Object();
person.name = 'Alex';
person.hi = function() {
	alert("Hi! I'm " + this.name + " .");
};

// another way to create an object
var person = new Object({
  name: 'Alex',
  hi: function() {
    alert("Hi! I'm " + this.name + " .");
  }
});


// creating a custom type
function Person(name) {
	this.name = name;
	this.hi = function() {
		alert("Hi! I'm " + this.name + " .");
	};
}

// create an instance pf Person
var person = new Person('Alex');

// check the constructor
person.constructor;

// using the constructor as a function i.e. without "new"
var person = Person('Alex');
person.name
name

// constructor Vs. prototype
function Person(name) {
	this.name = name;
	this.constructor_list = [];
}

Person.prototype.prototype_list = [];

obj1 = new Person('one');
obj2 = new Person('two');

obj1.constructor_list.push('test1');
obj2.constructor_list;

obj1.prototype_list.push('test2');
obj1.prototype_list;
obj2.prototype_list;


// inheritance using call()
function Person(first, last) {
	this.name = first + last;
}

function Staff(first, last, position) {
	Person.call(this, first, last);
	this.position = position;
}

// inheritance with __proto__
let a = {
	'a': 1,
	hi: function() {return this.a;}
};

a.__proto__;

let b = {
	'b': 1,
	__proto__: a
};

b.__proto__;
b.hi();


// inheritance using create()
let a = {
	'a': 1,
	hi: function() {return this.a;}
};

let b = Object.create(a);


// inheritance using "class"
class Person {
	constructor(name) {
		this.name = name;
	}

	hi() {
		console.log("Hi!");
	}
}


person = new Person('Alex');
person.hi();


// create a subclass
class Staff extends Person {
	constructor(name, grade) {
		super(name);
		this.grade = grade;
	}
}

let staff = new Staff('Alex', 2);
staff.hi();
staff.grade;
staff.name;