Get value between range?

[Physes]

Is it possible to get a secure random number within a certain range- i.e. 0-100?

[mkropat]

That's not really the purpose behind this library. It is more of a wrapper around the crypto API to make it consistent across platforms.

If you wanted to do this, here is a sketch of how you could leverage secureRandom to do it:

const getIntBetween = (lowerBoundInclusive, upperBoundInclusive) =>
  getInt(upperBoundInclusive - lowerBoundInclusive + 1) + lowerBoundInclusive;

const getInt = (upperBoundExclusive) => {
  if (upperBoundExclusive === 1) {
    return 0; // short-circuit to avoid calling secureRandom with `0`
  }

  const numBytes = Math.ceil(Math.log(upperBoundExclusive) / Math.log(256));
  const startOfBias = Math.pow(2, 8*numBytes) - Math.pow(2, 8*numBytes) % upperBoundExclusive;
  let randomNumber;
  do
  {
    randomNumber = byteArrayToInt(secureRandom(numBytes));
  } while (randomNumber >= startOfBias);
  return randomNumber % upperBoundExclusive;
};

const byteArrayToInt = (bytes=[]) => {
  let result = 0;
  let power = 1;
  for (let i = bytes.length - 1; i >= 0; i--) {
    result += bytes[i]*power;
    power *= 256;
  }
  return result;
};