Have you looked at Haxe (http://haxe.org/ http://haxe.org/)? It's supposed to have a decent type system, although I can't say how it compares to TypeScript's si

Have you looked at Haxe (http://haxe.org/ http://haxe.org/)? It's supposed to have a decent type system, although I can't say how it compares to TypeScript's since I've used neither of them. If you need a stronger type system, and you're already using TypeScript, take a look at FunScript (http://funscript.info/); http://funscript.info/); it uses the meta-programming features of F# to do strongly-typed JS (and TypeScript) code generation and interop with existing code.