Ah, the boolean saber technique

I don't understand it either. People are suggesting that [] is returned in place of null. but:

"test".match(/foo/ || []); // returns null, not []

[] is also a truthy value, not falsy:

if ([]) true // true

¬(¬A^¬B), something something my young apprentice.

These are new teachings! I will have to keep an eye out for errant + and ||. How would solve the riddle of the OR operator when it comes to horizontal awareness?

You're not going to get fib(500) with recursion.

This is the best solution, but the point was to do it backwards i think. :)

Nice! But it seems to have only passed 5 tests.