It's implementation, not part of standard. In this kata, you should not count on this number.

Yes, sometimes stalemate is the only way to win, if you make your opponent make stalemate.

Which input parameters (a,b,c) in this test exactly are?

Updated description about random order.

He cannot eat one cake, because you ate one cake on previous turn.

Rounding errors

Your solution is incorrect. Sorting is wrong when c < a < b.

There are no private members in javascript objects, so variables declared in object constructor's scope are used instead.

Yes, because you can choose who moves first

You should find strategy, how to decrease number of cakes without giving opponent chance to win. Each your move not only shortens cakes amount, but also prevents opponent from eating same number of cakes as you.

This happens if 2 cakes are left and you eat one of them. Try to avoid this situation.

Maybe you print result to terminal and don't return it?

Updated description. About three pairs it's stated in examples.

Where is eval?