Fast random number generator

FastRandom.js

/**
 * An extremely fast pseudorandom number generator. Note that we are using
 * this class to REPLACE Math.random :)
 *
 * Thanks to Doug Lea for help with this :)
 */
export class FastRandom {
  private next;

  /**
   * Creates a new random number generator with the given seed, or the current
   * time if no seed given.
   *
   * @param seed a number, or null/undefined to use the current time
   */
  constructor(seed : number = undefined) {
    this.seed(seed);
  }

  /**
   * Resets this random number generator with the given seed, or the current
   * time if no seed given.
   *
   * @param seed a number, or null/undefined to use the current time
   */
  seed(seed : number = undefined) {
    if (typeof seed === "undefined")
      seed = new Date().getTime();
    var next = seed;
    next ^= (next << 6);
    next ^= (next >>> 21);
    next ^= (next << 7);
    this.next = next;
  }

  /**
   * Returns the next pseudorandom number in this sequence.
   *
   * @returns {number} a float from 0 (inclusive) to 1 (exclusive)
   */
  nextFloat() {
    var ret = this.next;
    this.next ^= (this.next << 6);
    this.next ^= (this.next >>> 21);
    this.next ^= (this.next << 7);
    return (ret >>> 8) / (1 << 24);
  }
}

(function() {
  var rng = new FastRandom();
  Math["seedrandom"] = function(seed : number = undefined) {
    rng.seed(seed);
  };

  Math.random = function() {
    return rng.nextFloat()
  };
  rng.seed();
})();