Same problem with all dynamically-typed languages, really. It's too easy to write the wrong thing and not find out about it until you've written umpteen unit te

Same problem with all dynamically-typed languages, really. It's too easy to write the wrong thing and not find out about it until you've written umpteen unit tests. This can happen due to typos, refactoring, or whatever else. Only JavaScript is worse because it's weakly typed too, so it performs implicit coercions in an effort to make your code always do something (meaning your unit tests have to be very good to really ensure your functions do what you think they do). A static type system ensures that, at the very least, all the types line up at compile-time. You find type errors much faster than with a dynamically typed language, and this can guide a much less exhausting development cycle.