Use Object.assign for constant definitions.

[tschw]

See #8824

[mrdoob]

Thanks!

[mrdoob]

As far as I understand, this pattern:

THREE.RingGeometry.prototype=Object.create(THREE.Geometry.prototype);
THREE.RingGeometry.prototype.constructor=THREE.RingGeometry;

Can now be just this...

Object.assign( THREE.RingGeometry.prototype, THREE.Geometry.prototype );

Right?

[tschw]

@mrdoob

Object.assign( THREE.RingGeometry.prototype, THREE.Geometry.prototype );

Unfortunately it's not quite that simple: In case we use this scheme, we get false asking whether aRingGeometry instanceof THREE.Geometry, because

THREE.RingGeometry.prototype.constructor === THREE.RingGeometry &&
THREE.RingGeometry.prototype.__proto__.constructor  === Object

and not

THREE.RingGeometry.prototype.constructor === THREE.RingGeometry &&
THREE.RingGeometry.prototype.__proto__.constructor === THREE.Geometry &&
THREE.RingGeometry.prototype.__proto__.__proto__.constructor  === Object

.

So it's

THREE.RingGeometry.prototype =
        Object.assign( Object.create( THREE.Geometry.prototype ), {

    constructor: THREE.RingGeometry, // else it's THREE.Geometry

    /* ... */

} );

.

One could change .prototype.__proto__, but the MDN documentation reads:

Warning: Changing the [[Prototype]] of an object is, by the nature of how modern JavaScript engines optimize property accesses, a very slow operation, in every browser and JavaScript engine. The effects on performance of altering inheritance are subtle and far-flung, and are not limited to simply the time spent in obj.__proto__ = ... statement, but may extend to any code that has access to any object whose [[Prototype]] has been altered. If you care about performance you should avoid setting the [[Prototype]] of an object. Instead, create a new object with the desired [[Prototype]] using Object.create().

Warning: While Object.prototype.__proto__ is supported today in most browsers, its existence and exact behavior has only been standardized in the ECMAScript 6 specification as a legacy feature to ensure compatibility for web browsers. For better support, it is recommended that only Object.getPrototypeOf() be used instead.

So that's not really an option for us.

You can get around Object.create like done here, however, I have no clue why they actually do it (I believe this code may only be used when the "debug loader" is in effect - when compiled, the Closure compiler actually generates code that uses Object.create unless it can squash the inheritance altogether and if I'm not mistaken).

[mrdoob]

I see I see. As usual, thanks a ton for the explanations!

[tschw]

I had to correct above post; obj.prototype isn't meaningful. It's either ctor.prototype or obj.__proto__.