Javascript NaN

I just spent 30 minutes reading log files to find an actual bug that would've been prevented by a strong type system: Multiplying a coordinate by an array instead of an element of that array; Javascript helpfully gave me the result NaN and carried on instead of throwing an exception, because Javascript. I may put a few defensive asserts of Number.isInteger(n), Number.isFinite(x) in functions that process numbers.

This is the first such bug I've had in so long I can't think of the last. Many years not spent fighting BDSM type systems and slow-ass compilers, so I'm still happy with this choice.