Get random bigint value in range.

getRandomBigInt.mjs

/**
 * @param {number} byteLength A QuotaExceededError DOMException is thrown if the requested length is greater than 65536 bytes.
 * @returns {bigint}
 */
function getRandomBigIntByByteLength(byteLength) {
    const buffer = new Uint8Array(byteLength);
    crypto.getRandomValues(buffer);
    return buffer.reduce((prev, current) => (prev << 8n) + BigInt(current), 0n);
}

/**
 * Return random bigint (min <= value < max)
 * @param {bigint} min
 * @param {bigint} max
 */
export function getRandomBigInt(min, max) {
    if (min >= max) { throw RangeError("min value must be less than max value in getRandomBigInt arguments"); }
    const bitLength = BigInt((max - min).toString(2).length);
    const byteLength = Number((bitLength + 7n) / 8n);
    let random;
    do {
        random = getRandomBigIntByByteLength(byteLength) + min;
    } while (random >= max);
    return random;
}