pick.js

var MersenneTwister = require("mersenne-twister"),
  generator = new MersenneTwister();

// @todo Assert state/chain transitions

function randomNumberBetween(min, max, nonZero) {
  var number;

  do {
    number = Math.floor(generator.random() * (max - min + 1)) + min;
  } while (nonZero && number === 0);

  return number;
}

function Slots(count) {
  this._count = count;
}

Slots.prototype.toArray = function () {
  return this._slots.slice(0);
};

Slots.prototype.pairsOf = function () {
  this._count *= 2;
  return this;
};

Slots.prototype.triplesOf = function () {
  this._count *= 3;
  return this;
};

Slots.prototype.numbersBetween = function (min, max) {
  this._slots = this._slots || [];

  for (var i = 0; i < this._count; i++) {
    if (this._or && generator.random() > 0.5) {
      continue;
    }
    this._slots[i] = randomNumberBetween(min, max, this._nonZero);
  }

  this._or = false;

  return this;
};

Slots.prototype.letters = function () {
  this._slots = this._slots || [];

  var a = "A".charCodeAt(0),
    z = "Z".charCodeAt(0);

  for (var i = 0; i < this._count; i++) {
    if (this._or && generator.random() > 0.5) {
      continue;
    }
    this._slots[i] = String.fromCharCode(randomNumberBetween(a, z));
  }

  this._or = false;

  return this;
};

Slots.prototype.wordFrom = function (wordList) {
  this._slots = this._slots || [];

  for (var i = 0; i < this._count; i++) {
    var word = wordList[Math.floor(generator.random() * wordList.length)];
    this._slots.push.apply(this._slots, word.split(""));
  }

  return this;
};

Slots.prototype.from = function (factory) {
  this._slots = this._slots || [];

  for (var i = 0; i < this._count; i++) {
    if (this._or && generator.random() > 0.5) {
      continue;
    }
    this._slots[i] = factory();
  }

  this._or = false;

  return this;
};

Slots.prototype.or = function () {
  this._or = true;
  return this;
};

Slots.prototype.nonZero = function () {
  this._nonZero = true;
  return this;
};

exports.seed = function (seed) {
  generator.init_seed(seed);
};

exports.exactly = function (count) {
  return new Slots(count);
};

exports.between = function (min, max) {
  return new Slots(randomNumberBetween(min, max));
};