Determine if a string is an IPv4 or IPv6 multicast or unicast ip address.

MulticastTest.js

// Tests the ipAddress string and returns whether it's unicast or multicast.
function getNetworkMode(ipAddress) {

  if(ipAddress.contains(':')) {
    // IPv6
    if(/^ff\w{2}:/i.test(ipAddress))
      return "Multicast";
    
    return "Unicast";
  }

  // an IPv4 address or a hostname

  var octetMatch = ipAddress.match(/^(\d+)\./);
  if(octetMatch == null) // ipAddress is a hostname
    return "Unicast";

  // IPv4 address
  var firstOctet = octetMatch[1];
  if(224 <= firstOctet && firstOctet <= 239)
    return "Multicast";

  return "Unicast";
}