Fibonacci in JS

fibonacci.js

function fib(n) {
  var numbers = [0, 1] // initialise the array
  while (n > 1) {
    var new_num = numbers[0] + numbers[1];
    numbers.shift(); // drop the first element
    numbers.push(new_num); // add the new element to the end
    n -= 1;
  }
  return numbers[n];
}