OLOO (objects linked to other objects) pattern explored (with comparison to the prototype style of the same code)

ex1-prototype-style.js

function Foo(who) {
	this.me = who;
}

Foo.prototype.identify = function() {
	return "I am " + this.me;
};

function Bar(who) {
	Foo.call(this,"Bar:" + who);
}

Bar.prototype = Object.create(Foo.prototype);
Bar.prototype.constructor = Bar;    // "fixes" the delegated `constructor` reference

Bar.prototype.speak = function() {
	alert("Hello, " + this.identify() + ".");
};

var b1 = new Bar("b1");
var b2 = new Bar("b2");

b1.speak(); // alerts: "Hello, I am Bar:b1."
b2.speak(); // alerts: "Hello, I am Bar:b2."

// some type introspection
b1 instanceof Bar; // true
b2 instanceof Bar; // true
b1 instanceof Foo; // true
b2 instanceof Foo; // true
Bar.prototype instanceof Foo; // true
Bar.prototype.isPrototypeOf(b1); // true
Bar.prototype.isPrototypeOf(b2); // true
Foo.prototype.isPrototypeOf(b1); // true
Foo.prototype.isPrototypeOf(b2); // true
Foo.prototype.isPrototypeOf(Bar.prototype); // true
Object.getPrototypeOf(b1) === Bar.prototype; // true
Object.getPrototypeOf(b2) === Bar.prototype; // true
Object.getPrototypeOf(Bar.prototype) === Foo.prototype; // true

ex2-oloo-style.js

var Foo = {
	Foo: function(who) {
		this.me = who;
		return this;
	},
	identify: function() {
		return "I am " + this.me;
	}
};

var Bar = Object.create(Foo);

Bar.Bar = function(who) {
	// "constructors" (aka "initializers") are now in the `[[Prototype]]` chain,
	// so `this.Foo(..)` works easily w/o any problems of relative-polymorphism
	// or .call(this,..) awkwardness of the implicit "mixin" pattern
	this.Foo("Bar:" + who);
	return this;
};

Bar.speak = function() {
	alert("Hello, " + this.identify() + ".");
};

var b1 = Object.create(Bar).Bar("b1");
var b2 = Object.create(Bar).Bar("b2");

b1.speak(); // alerts: "Hello, I am Bar:b1."
b2.speak(); // alerts: "Hello, I am Bar:b2."

// some type introspection
Bar.isPrototypeOf(b1); // true
Bar.isPrototypeOf(b2); // true
Foo.isPrototypeOf(b1); // true
Foo.isPrototypeOf(b2); // true
Foo.isPrototypeOf(Bar); // true
Object.getPrototypeOf(b1) === Bar; // true
Object.getPrototypeOf(b2) === Bar; // true
Object.getPrototypeOf(Bar) === Foo; // true

@GodefroyClair

The reason is that the real inheritance pattern ... relies on copying where as the one implemented in js relies on linking

Great explanation of the concept! Way to go!

I prefer composition over inheritance. Carrying all the forest doesn't make sense.
The difference is INHERITANCE is when you design your types around what they are and COMPOSITION is when you design your types around what they do.

I believe through this practice the key takeaway is Behavior Delegation of objects linking to other objects.

OLOO for the win. Also add this to Foo:

  [Symbol.hasInstance](instance) {
    return this.isPrototypeOf(instance)
  }

so this will work fine too:

b1 instanceof Bar; // true
b2 instanceof Bar; // true
b1 instanceof Foo; // true
b2 instanceof Foo; // true