Core: make Vector and Matrix .is* property non-enumerable

[marcofugaro]

Related issue: Fixes #24167 as proposed by #24167 (comment)

Description

Since we decided not to support .toJSON() for Vector and Matrix classes (#24172), let's support the JSON.stringify() serialization.

Setting the prototype in the constructor allows for tree-shaking and makes the .isVector3 property non-enumerable, so it doesn't show up in the JSON.stringify().

This does not make a breaking change as opposed to the instanceof method 😬

[mrdoob]

Interesting...

This does not make a breaking change as opposed to the instanceof method 😬

I'm curious about how much of a breaking change that'd be though...

[marcofugaro]

I'm curious about how much of a breaking change that'd be though...

You mean if people are using .isVector3? I don't really know but I believe some people out there might have it deep in their code haha

[Dannie226]

If anything, people would be using the .isVector3 property for type checking. Given that checking a boolean would probably be faster in js than comparing two objects, I tend to prefer using the .is* properties, but, it is a simple change (find .isVector3, replace with instanceof Vector3/THREE.Vector3).

[mrdoob]

Alright. Lets go with this.
However, this wins the most-weird-thing-in-the-library award imho 😁

[mrdoob]

Thanks!