code from jspoland2020 JavaScript talk

jspoland2020.js

// // value of 'this' depends on how  you are calling the function 

var Dog = {
    name :'foo',
    eat : function(){
        console.log(this);
    }
}

var Cat = {
    name :'my cat'
}

function Product(){
    console.log(this);
    return 9; 
}

let a = Product() ; // function invocation pattern ,  value of 'this' is global object 
let b = new Product(); // constructor invocation pattern , value of 'this' is newly created object 
console.log(b);

Dog.eat(); // method value of 'this' is object before dot

Dog.eat.call(Cat); // apply, call, bind i.e indirect invocation pattern - this is always the first argument in the function

// __proto__ to link object 

var Animal = {
    name:'foo',
    age : 9
}

var Dog = {
    owner : 'koo',
    canRun : true 
}

Dog.__proto__ = Animal; 

Object.defineProperty(Dog,'owner',{enumerable:false});

for(var p in Dog){
    //console.log(Dog[p]);
    console.log(p);
}

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

// There are four ways object can be created in JavaScript 

// object literal 
// var Dog = {

// }

// Object.create 

var Cat = Object.create(Dog)

// use class 

function Product (title,price){
    this.title = title; 
    this.price = price; 
}

Product.prototype.color = 'blue'; 
//console.log(Product.prototype);

 var p1 = new Product('p1',90);
 var p2 = new Product('p2',20);

p1.color = "red";
console.log(p1.__proto__.color);
console.log(p2.color);
console.log(p1.constructor);
console.log(p2.constructor);

// when you create an object in javascript using constructor, that object is linked to prototype of the construcrtor


console.log(p1.constructor.prototype == p2.constructor.prototype);
console.log(p1.constructor.prototype == p1.__proto__);