I was building an app with validation in both the browser and a Node.js server. Wanted one set of rules that worked in both places, but also wouldn't lock me into JS forever. A C# or Go server could be useful down the line for speed, and I'd rather not rewrite all my validation when that happens.
So, I built AnyVali — write schemas natively in your language, export to JSON, import anywhere else. All 10 SDKs pass the same test suite so behavior is identical everywhere. No runtime dependencies in most of them. Still early but the core is solid — install it, try it out, and let me know what you think.