JAVASCRIPT

random bigint javascript

/** Generates BigInts between low (inclusive) and high (exclusive) */
function generateRandomBigInt(lowBigInt, highBigInt) {
  if (lowBigInt >= highBigInt) {
    throw new Error('lowBigInt must be smaller than highBigInt');
  }

  const difference = highBigInt - lowBigInt;
  const differenceLength = difference.toString().length;
  let multiplier = '';
  while (multiplier.length < differenceLength) {
    multiplier += Math.random()
      .toString()
      .split('.')[1];
  }
  multiplier = multiplier.slice(0, differenceLength);
  const divisor = '1' + '0'.repeat(differenceLength);

  const randomDifference = (difference * BigInt(multiplier)) / BigInt(divisor);

  return lowBigInt + randomDifference;
}