Where the `prototype` property is defined

Question

Well, all the time i supposed that prototype property exists at all objects. But after one of job interview i came home and open chrome console

window.prototype
**undefined**

WTF?

Object.prototype
**Object {}**

OK

var a = {};
a.prototype
**undefined**

var a = function(){}
a.prototype
**Object {}**

I've read https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/prototype several times but still not clear. Can anybody explain?

Thanx

P.S. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/prototype

All objects in JavaScript are descended from Object; all objects inherit methods and properties from Object.prototype, although they may be overridden (except an Object with a null prototype, i.e. Object.create(null)

window is Object, so it must have prototype property

Answer 1

The object an instance inherits from, its prototype, is stored in an internal property, [[Prototype]]. Its value can be retrieved with Object.getPrototypeOf() (in ES5-compatible engines).

console.log(Object.getPrototypeOf(window));
// Window { ... }

var a = {};
console.log(Object.getPrototypeOf(a));
// Object { ... }

Only functions explicitly have a prototype property:

console.log(typeof Object);
// 'function'

And, the value of the prototype is just used to set the value of the instance's [[Prototype]] when a new instance is created.

function Foo() {}
var bar = new Foo();

console.log(Foo.prototype === Object.getPrototypeOf(bar)); // true