One must simply cherish your solution soooo much! Enjoyable, elegant, briliant!

So elegant. Congratulations!

I'm in the same boat as you. I knew it could be done, but I just couldn't wrap my head around a recursive solution.

So good. How do I master the recurrrrsssiooonnn. I got as far as writing countArara(n-2) then did it w/o recursion!

Just look at my solution. I did it.

This is an issue with how JavaScript handle floats. You would have the same result when using Math.round:

Math.round(1.005 * 100) / 100 === 1

Computing accurate roundings would make an interesting kata, but here I think it is out of scope, as it would add a lot of work to handle that specific case.

Problem: Try [ [0,0] , [0,1.005] ]
It should return "1.01" but returns "1.00" instead.
This is a problem of JavaScript that was not covered in the test cases.
Check this out:
http://stackoverflow.com/questions/11832914/round-to-at-most-2-decimal-places-in-javascript
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/round

Wow, quite clever. I had now idea hypot existed! Well done!

so cool