Make Freezer extendable (closes #22)

[kuraga]

1. We extend Freezer.prototype but not replace it.
2. We have to restore non-enumerable members of Freezer.prototype we need.
   The one is non-enumerable member of Freezer.prototype is Freezer.prototype.constructor.

[marquex]

Cool, this solution is simple and elegant! I will commit it later when I get out of work.

[kuraga]

@marquex @arqex ,
Note there is more elegant (all tests are green):

diff --git a/src/freezer.js b/src/freezer.js
index ed9a488..2c72cff 100644
--- a/src/freezer.js
+++ b/src/freezer.js
@@ -65,7 +65,7 @@ var Freezer = function( initialValue, mutable ) {
        this._events = [];
 }

-Freezer.prototype = Utils.createNonEnumerable({}, Emitter);
+Freezer.prototype.__proto__ = Emitter;
 //#build

 module.exports = Freezer;

But this way is not standard-compliant (precise: is not ES5-compliant, but it is ES6-compliant because __proto__ has been introduced in ES6).

Another side you use __proto__ here.

[kuraga]

See #27 for it

[arqex]

Hi @kuraga

Freezer should work in most browsers, and unfortunatelly __proto__ is not available in IE<11.

It is true that it is used by freezer to extend arrays, but there is a fallback for the browsers that don't support it. That's why I think that using __proto__ is not the best way of setting the constructor method.

I would do something like:

Freezer.prototype = Utils.createNonEnumerable({constructor: Freezer}, Emitter);

[kuraga]

@marquex @arqex
This PR is like you say. Merge?

[arqex]

It doesn't work if the constructor is not enumerable?

[kuraga]

Ah, now I understand what do you mean. I just want to use Freezer.prototype as a Utils.createNonEnumerable's first argument but not {}. Freezer.prototype may be non-empty! What do you think?

[kuraga]

So I want something like

// object_assign is like Object.assign: it merges arguments in one object
var newPrototype = object_assign(Freezer.prototype, {constructor: Freezer});
Freezer.prototype = Utils.createNonEnumerable(newPrototype, Emitter);

[arqex]

Sure, createNonEnumerable creates an object with the non enumerable properties passed as the first parameter, and with the prototype passed as the second.

So a freezer prototype would be:

Freezer.prototype = Utils.createNonEnumerable({constructor: Freezer}, Emitter);

// Prototoype
Freezer.prototype; // { constructor: Freezer } 
Freezer.prototype.prototype: // Emitter

It should work with ES6, shouldn't it?

[kuraga]

I'm talking about one thing only: first argument of Utils.createNonEnumerable should contain Freezer.prototype (and, maybe, something more). Now (in master) it is {} and doesn't contain Freezer.prototype. I think it's incorrect.

[kuraga]

And in this line:

Freezer.prototype = Utils.createNonEnumerable({constructor: Freezer}, Emitter);

first argument ({constructor: Freezer}) doesn't contain Freezer.prototype. Isn't it bad?

[kuraga]

Do you see what I changed in THIS (68) line? That's I'm talking about.

[kuraga]

Everything work without this change! But I think this change is right!!!

[arqex]

There is nothing bad with that. In fact, until that line is executed Freezer.prototype is nothing but an empty object.

But we really don't care about what the prototype was because we are setting a new one, that is what Freezer.prototype = Utils.createNonEnumerable({}, Emitter); is doing now.

[kuraga]

Freezer.prototype is nothing but an empty object.

It is empty for me but is it always guaranteed to be empty?

[kuraga]

Another side, its enumerable part is guaranteed empty... Ok, sorry for my fault brainstorm.

One moment.

[arqex]

Sure, it is guaranteed. Freezer is a function defined just in the previous instruction.

[kuraga]

Close in favour of #29