Rock paper scissors

document.write(
(function(a, y) {
  x = a.indexOf(y);
  return( [ "tie", a.pop(), a[y] ][
    !!(x ^ y) << !!(x ^ ( (y+1) % 3 ) )
  ]);
})(
    ["scissors", "paper", "rock", prompt("Do you choose rock, paper or scissors?")],
    Math.round(Math.random()*10)%3)
);