fib

gistfile1.txt

var initialFirst = 0;
var initialLast = 1;
var index = 0;
var calcFib = function selfCall (num) {
  if (num < 1) return;
  index++;
  var result = initialFirst + initialLast;
  initialFirst = initialLast;
  initialLast = result;

  if ((num - 1) === index) {
    return result;
  }
  return selfCall(num);
};

function fib(count) {
  if (count < 2) {
    return count;
  }
  return fib(count - 1) + fib(count - 2);
}