/**

* ***********

* Prototypes:

* ***********

* means Parent(it is just a regular object)

* Every object has a prototype except root

*

* *************************

* Prototypical Inheritence:

* *************************

*

* */

let x = {};

let y = {};

console.log(Object.getPrototypeOf(x)===Object.getPrototypeOf(y));

console.log(x.__proto__===y.__proto__); //This is deprecated recommended to be no use

//here every object is inherited from a prototype:parent object i.e Object

//x-->Object(__proto__) - Prototype

//y--> Object(__proto__)- Prototype

/**Multilevel Inheritence */

function Circle(radius){

//Instance members

this.radius = radius;

this.draw = function (){

console.log('draw');

}

}

const circle = new Circle(5);

console.log(Object.getPrototypeOf(circle));

console.log(Object.getPrototypeOf(circle)===Object.getPrototypeOf(y));

console.log(circle.__proto__===y.__proto__); //This is deprecated recommended to be no use

//Now let us check one level up

// we can easily verify here multilevel inheritence where circle-->Circle-->Object

console.log(circle.__proto__.__proto__===y.__proto__);

/**Property Descriptors */

let person = {name:'Sumit'};

let objectBase = Object.getPrototypeOf(person);

let descriptor = Object.getOwnPropertyDescriptor(objectBase, 'toString');

console.log(descriptor);

Object.defineProperty(person, 'name', {

writable:false, // we cannot write

enumerable:true, // we cannot iterate

configurable:false // we cannot configure the property eg: can't delete

});

person.name = 'JOHN';

console.log(person);

console.log(Object.keys(person));

delete person.name;

console.log(person);

let nameDescriptor = Object.getOwnPropertyDescriptor(person, 'name');

console.log(nameDescriptor);

/**Constructor Prototypes */

console.log(circle.__proto__ === Circle.prototype);

/**Prototype and Instance members*/

//Prototype members

Circle.prototype.draw1 = function(){

console.log('draw1');

}

const c1 = new Circle(1);

console.log(c1);

console.log(c1.__proto__);

console.log(c1.__proto__.draw1());

console.log(c1.draw1());

/**Iterating instance and Prototype members */

//it will only return keys associated to the Circle object (Instance memebers)not __proto__ object(Prototype members)

console.log(Object.keys(c1)); //[ 'radius', 'draw' ] - draw1 is not available because its a prototype's method

for(let key in c1) console.log(key); // it returns instance + prototype memebers

console.log(c1.hasOwnProperty('radius')); // instance memeber : true

console.log(c1.hasOwnProperty('draw')); // instance memeber : true

console.log(c1.hasOwnProperty('draw1'));// Prototype memeber : false

/**We can extend built in object

* but

* Avoid extending built in objects:

* Don't modify object you don't own

* */