> I am not opposed to adding strong type checking to JavaScript, but Typescript ain't it.

If you are curious about this, you might be interested in checking out Haxe [0]. It has static typing, type inference, pattern matching [1] (maybe not on par with ML languages, but still good), and can transpile to multiple targets [2] including JS.

[0]: https://haxe.org [1]: https://haxe.org/manual/lf-pattern-matching.html [2]: https://haxe.org/documentation/introduction/compiler-targets...