UnityEngine.Random on JavaScript

UnityEngine_Random.js

class UnityEngine_Random {
  /**
   * @type {number[]}
   */
  a = [1234, 3159640283, 3392860520, 3460949513];

  /**
   * @param {number} seed
   */
  initState(seed) {
    let n = BigInt(seed >>> 0) & 4294967295n;
    this.a[0] = Number(n);

    for (let i = 0; i < 3; ++i) {
      n = (1812433253n * n + 1n) & 4294967295n;
      this.a[i + 1] = Number(n);
    }
  }

  /**
   * @returns {number}
   */
  xorshift128() {
    const t = this.a[0] ^ (this.a[0] << 11);
    this.a[0] = this.a[1];
    this.a[1] = this.a[2];
    this.a[2] = this.a[3];
    this.a[3] = (this.a[3] ^ (this.a[3] >>> 19) ^ t ^ (t >>> 8)) >>> 0;
    return this.a[3];
  }

  /**
   * @param {number} min
   * @param {number} max
   * @returns {number}
   */
  randomRange(min, max) {
    const r = (this.xorshift128() & 0x7fffff) * 0.0000001192093;
    return min * r + max * (1 - r);
  }

  /**
   * @param {number} min
   * @param {number} max
   * @returns {number}
   */
  randomRangeInt(min, max) {
    if (min < max) {
      return min + (this.xorshift128() % (max - min));
    }

    if (min > max) {
      return max + (this.xorshift128() % (min - max));
    }

    return min;
  }
}