Normal Distribution in javascript

NormalDistribution.ts

/**
 * https://en.wikipedia.org/wiki/Marsaglia_polar_method
 * 
 * @param {*} mean Mittel
 * @param {*} sd Spreitzung
 */
export function NormalDistribution(mean, sd) {
    this._cache = [];
    this.mean = mean;
    this.sd = sd;
}
NormalDistribution.prototype._fill = function () {
    let u, v, q, p
    do {
        u = 2.0 * Math.random() - 1;
        v = 2.0 * Math.random() - 1;
        q = u * u + v * v;
    } while (q >= 1.0 || q == 0.0);

    p = Math.sqrt(-2 * Math.log(q) / q);
    let x1 = u * p;
    let x2 = v * p;
    this._cache.push(x1, x2);
};
NormalDistribution.prototype.next = function () {
    if (this._cache.length === 0) {
        this._fill();
    }
    var z = this._cache.pop();
    return (z * this.sd) + this.mean;
};

/**
 * @param {*} mean Mittel
 * @param {*} sd Spreitzung
 */
export function EvenlyDistribution(mean, sd) {
    this.diff = 2 * sd;
    this.shift = mean - sd;
}
EvenlyDistribution.prototype.next = function () {
    return Math.random() * this.diff + this.shift
};