Javascript UUIDs

uuids.js

function uuids (count, seed) {
  var pattern = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx';
  var _uuids = [];


  if (count === undefined) {
    count = 1;
  }

  if (seed === undefined) {
    seed = 1;
  }

  if (count < 1 && count > 0) {
    seed = count;
    count = 1;
  }

  if (count <= 0) {
    throw 'Count should be greater than 0';
  }

  if (seed <= 0 || seed > 1) {
    throw 'Seed should be in greater than 0 and less than or equal to 1';
  }

  function getUUID(pattern) {
    // Borrowed from http://stackoverflow.com/questions/105034/how-to-create-a-guid-uuid-in-javascript/2117523#2117523
    return pattern.replace(/[xy]/g, function(character) {
      var seeded_rand;

      var raw_rand = Math.random();
      var max = Math.max(raw_rand, seed);
      var min = Math.min(raw_rand, seed);

      if (max === 0) {
        seeded_rand = 0;
      } else {
        /* This is required to ensure that either of the numbers don't decrease
           the range of set size. That is why seed * raw_rand will not be right. */
        seeded_rand = min/max;
      }

      var ranged_rand = seeded_rand*16|0;
      var replacement = character === 'x' ? ranged_rand : (ranged_rand & 0x3|0x8);

      return replacement.toString(16);
    });
  }


  // Fill up uuids upto the count which is asked for
  while(_uuids.push(getUUID(pattern)) < count) {
  }

  return _uuids;
};