Generate permutations of an array in lexicographic order (using http://en.wikipedia.org/wiki/Permutation#Generation_in_lexicographic_order)

permutation.js

function next(start) {
  start = start;

  //Find the largest index k such that a[k] < a[k + 1].
  var k = start.length - 2;
  while (k >= 0 && start[k] >= start[k + 1]) k--;
  //If no such index exists, the permutation is the last permutation.
  if (k < 0) return null;

  //Find the largest index j such that a[k] < a[j].
  //Since k + 1 is such an index, j is well defined and satisfies k < j.
  var j = start.length - 1;
  while (j > k && start[k] >= start[j]) j--;
  if (j <= k) throw new Error('k should never be greater than j');

  //Swap a[k] with a[j].
  var temp = start[k];
  start[k] = start[j];
  start[j] = temp;

  //Reverse the sequence from a[k + 1] up to and including the final element.
  var result = [];
  for (var i = 0; i <= k; i++) {
    result.push(start[i]);
  }
  for (var i = start.length - 1; i > k; i--) {
    result.push(start[i]);
  }
  return result;
}
var str = '0123456789'.split('');
for (var i = 1; i < 1000000; i++) str = next(str);