javascript 种子で乱数固定可能な乱数生成クラス

Posted 2021-05-03

// https://sbfl.net/blog/2017/06/01/javascript-reproducible-random/
class Random {
  constructor(seed = 88675123) {
    this.x = 123456789;
    this.y = 362436069;
    this.z = 521288629;
    this.w = seed;
  }
  // XorShift
  next() {
    let t;
    t = this.x ^ (this.x << 11);
    this.x = this.y; this.y = this.z; this.z = this.w;
    return this.w = (this.w ^ (this.w >>> 19)) ^ (t ^ (t >>> 8)); 
  }
  // min以上max以下の乱数を生成する
  nextInt(min = 0, max = 100000) {
    const r = Math.abs(this.next());
    return min + (r % (max + 1 - min));
  }
}