rotate.js

_.rotate = function(array, count) {
  var array = _.clone(array),
    count = count || 1;
  if (Math.abs(count) > array.length/2) count = 0 - count;
  if (count < 0)
    while (count++) array.unshift(array.pop());
  else
    while (count--) array.push(array.shift());
  return array;
};