Wow! How did you manage that?

The description says "only non-negative numbers are passed". So there's no problem here :)

Good catch, didn't pay attention to it. Thank you, corrected. :)

I like that NaN is treated as a number. I was doing a different kata that had NaN in the test cases and got temporarily stumped on it, I assumed NaN was indeed not a number...

It might be more than just a JS quirk. Python handles NaN similarly:

x = float('NaN')
print x # prints nan
type(x) # float

I guess NaN is also defined by an IEEE standard. http://en.wikipedia.org/wiki/NaN

NaN is actually a number. One of JavaScript's little quirks. I threw that test case in there just to keep people on their toes!

Exactly, there should be test cases for leading or trailing dots.

Test added, thank you!