PropUtils type checking not working properly in SvelteKit dev mode with few routes

[vatro]

I ran into this strange issue while refactoring test scenes, where type checking via PropUtils is not working in dev mode if there are only few routes (one-two links to scenes as a part of a side navigation) pointing to sveltehree-scenes. E.g. with:

svelthree/src/utils/PropUtils.ts

Lines 56 to 58 in 754a5f1

	public static isVector3(p: any): boolean {
	return p?.constructor === Vector3
	}

p?.constructor === Vector3 would be false.

If there are more routes, everything is ok in dev mode.
Also, with a built project, everything is ok in preview mode.

I'm not sure why this is happening, I guess it has something to do with the SvelteKit router / hmr in dev mode.
Changing the above to p?.constructor.name === "Vector3" works as a ducktape-fix.

After finding out what's going on, I've realized that I could generally improve type checking in PropUtils a bit by:

• using Array.isArray() which seems to be the fastest method for Array type checking (see https://www.measurethat.net/Benchmarks/Show/2872/0/isarray#latest_results_block)
• using three's .is* properties
  • see Core: Switch to this.is* = true. mrdoob/three.js#24047
  • see Core: make Vector and Matrix .is* property non-enumerable mrdoob/three.js#24219
• refactor some parts / add new functions in order to avoid redundant checks (like e.g. checking if something is an array two times)