calculateIpv4Subnet.js

export function calculateIpv4Subnet(ipAddress, subnetMask) {
    // helper functions
    const numbersArrayFromString = v => v.split('.').map(v => parseInt(v));
    const numberBinaryAsString = v => (v >>> 0).toString(2).padStart(8, '0');
    const addressBinaryAsString = v => numbersArrayFromString(v).map(numberBinaryAsString).join('');
    const addressAsNumber = v => parseInt(addressBinaryAsString(v), 2);
    const addressStringFromNumber = v => [24, 16, 8, 0].map(shift => (v >>> shift) & 255).join('.');

    ipAddressNumber = addressAsNumber(ipAddress);
    subnetMaskNumber = addressAsNumber(subnetMask);
    const networkAddress = ipAddressNumber & subnetMaskNumber;
    const amountOfHostsPerSubnet = parseInt(addressBinaryAsString(subnetMask).replace(/^1*/, '1'), 2);
    const broadcastAddress = networkAddress + amountOfHostsPerSubnet - 1;
    const isCidr32 = subnetMask === '255.255.255.255';
    const firstUsableIpAddress = isCidr32 ? networkAddress : networkAddress + 1;
    const lastUsableIpAddress = isCidr32 ? broadcastAddress : broadcastAddress - 1;
    const cidr = addressBinaryAsString(subnetMask).replace(/0{1,}$/, '').split('').length;
    const amountOfUsableIpAddresses = isCidr32 ? 0 : amountOfHostsPerSubnet - 2;

    return {
        ipAddress: ipAddress,
        subnetMask: subnetMask,
        networkAddress: addressStringFromNumber(networkAddress),
        broadcastAddress: addressStringFromNumber(broadcastAddress),
        amountOfIpAddresses: amountOfHostsPerSubnet,
        amountOfUsableIpAddresses: amountOfUsableIpAddresses,
        firstUsableIpAddress: amountOfUsableIpAddresses > 0 ? addressStringFromNumber(firstUsableIpAddress) : null,
        lastUsableIpAddress: amountOfUsableIpAddresses > 0 ? addressStringFromNumber(lastUsableIpAddress) : null,
        cidr: `/${cidr}`,
    };
}