q4 answer

function validateIPv4Address(address) {
  const arrayedAddress = address.split('.');
  if (arrayedAddress.length !== 4) {
    return false;
  }

  const invalidOctet = arrayedAddress.filter(octet => parseInt(octet, 10) < 0 || parseInt(octet, 10) > 255);

  return invalidOctet.length === 0;
}

function clasifyIPv4Address(address) {
  const subnetClasses = {
    A: {
      lowest: 0,
      highest: 127,
    },
    B: {
      lowest: 128,
      highest: 191,
    },
    C: {
      lowest: 192,
      highest: 223,
    },
    D: {
      lowest: 224,
      highest: 239,
    },
    E: {
      lowest: 240,
      highest: 255,
    },
  };

  if (validateIPv4Address(address)) {
    const addressPointer = parseInt(address.split('.')[0]);
    for (let subnetClass in subnetClasses) {
      const lowest = subnetClasses[subnetClass].lowest;
      const highest = subnetClasses[subnetClass].highest;
      if (addressPointer >= lowest && addressPointer <= highest) {
        return subnetClass;
      }
    }
  }

  return new Error('Invalid IPv4 address');
}