prototype chain

gistfile1.js

var assert = require('assert');

// Object -> Function.prototype -> Object.prototype -> null
assert.strictEqual(Object.__proto__, Function.prototype);
assert.strictEqual(Function.prototype.__proto__, Object.prototype);
assert.strictEqual(Object.prototype.__proto__, null);

// Function -> Function.prototype -> Object.prototype -> null
assert.strictEqual(Function.__proto__, Function.prototype);
assert.strictEqual(Function.prototype.__proto__, Object.prototype);
assert.strictEqual(Object.prototype.__proto__, null);

// o -> Object.prototype -> null
var o = {};
assert.strictEqual(o.__proto__, Object.prototype);
assert.strictEqual(Object.prototype.__proto__, null);

// Hoge -> Function.prototype -> Object.prototype -> null
var Hoge = function () {};
assert.strictEqual(Hoge.__proto__, Function.prototype);
assert.strictEqual(Function.prototype.__proto__, Object.prototype);
assert.strictEqual(Object.prototype.__proto__, null);

// hoge -> Hoge.prototype -> Object.prototype -> null
var hoge = new Hoge();
assert.strictEqual(hoge.__proto__, Hoge.prototype);
assert.strictEqual(Hoge.prototype.__proto__, Object.prototype);
assert.strictEqual(Object.prototype.__proto__, null);

// foo -> Foo.prototype (hoge) -> Hoge.prototype -> Object.prototype -> null
var Foo = function () {};
Foo.prototype = hoge;
var foo = new Foo();
assert.strictEqual(foo.__proto__, Foo.prototype);
assert.strictEqual(Foo.prototype, hoge);
assert.strictEqual(hoge.__proto__, Hoge.prototype);
assert.strictEqual(Hoge.prototype.__proto__, Object.prototype);
assert.strictEqual(Object.prototype.__proto__, null);

// bar -> Foo.prototype (hoge) -> Hoge.prototype -> Object.prototype -> null
var Bar = function () {};
var bar = new Bar();
bar.__proto__ = Foo.prototype;
assert.strictEqual(bar.__proto__, Foo.prototype);
assert.strictEqual(Foo.prototype, hoge);
assert.strictEqual(hoge.__proto__, Hoge.prototype);
assert.strictEqual(Hoge.prototype.__proto__, Object.prototype);
assert.strictEqual(Object.prototype.__proto__, null);

// baz -> Baz.prototype -> Foo.prototype (hoge) -> Hoge.prototype -> Object.prototype -> null
var Baz = function () {};
Baz.prototype.__proto__ = Foo.prototype;
var baz = new Baz();
assert.strictEqual(baz.__proto__, Baz.prototype);
assert.strictEqual(Baz.prototype.__proto__, Foo.prototype);
assert.strictEqual(Foo.prototype, hoge);
assert.strictEqual(hoge.__proto__, Hoge.prototype);
assert.strictEqual(Hoge.prototype.__proto__, Object.prototype);
assert.strictEqual(Object.prototype.__proto__, null);