js prototype and __proto__

function / class

null

reference prototype

Object.prototype

reference constructor

function Object

object

when class A

when class B

reference __proto__

class A {}A.idA = 'class A';class B extends A{}B.idB = 'class B extends A';var prototypeOfA = A.prototype;prototypeOfA.idAp = 'A.prototype';var prototypeOfB = B.prototype;prototypeOfB.idBp = 'B.prototype';var instanceOfB = new B();instanceOfB.idBi = 'B.instance';var assert = console.assert;assert(B.__proto__ === A);assert(B.prototype.__proto__ === A.prototype); assert(instanceOfB.__proto__ === B.prototype); assert('idBp' in instanceOfB);assert('idAp' in instanceOfB);assert('idA' in B);

when new B()

function Function

object B.prototype{idBp: 'B.prototype'}

Foo.prototype

function Foo

object A.prototype{idAp: 'A.prototype'}

class B extends Afunction B(){idB: 'class B ext. A'}

instanceof B{idBi: 'instanceof B}

when extends A

class Afunction A(){idA: 'class A'}

Function.prototypefunction f() {...}