AI solution for JavaScript Coding Question on BFE.dev
98. validate an IP address

Here's one possible solution in JavaScript:

function isValidIPAddress(str) {
  // Check for a valid IPv4 address
  if (/^(\d{1,3}\.){3}\d{1,3}$/.test(str)) {
    const octets = str.split('.');
    return octets.every(octet => parseInt(octet, 10) <= 255);
  }
  
  // Check for a valid IPv6 address
  if (/^([\da-f]{1,4}:){7}[\da-f]{1,4}$/.test(str)) {
    return true;
  }

  return false;
}

This function uses regular expressions to check if the input string matches either the format of an IPv4 address or an IPv6 address.

For IPv4 addresses, we use the regular expression ^(\d{1,3}\.){3}\d{1,3}$, which matches strings that contain exactly 4 sets of digits separated by a period. We then split the string into separate "octets" and verify that each one is a valid number between 0 and 255.

For IPv6 addresses, we use the regular expression ^([\da-f]{1,4}:){7}[\da-f]{1,4}$, which matches strings that contain exactly 8 sets of hexadecimal digits separated by a colon. We then simply return true, as no further validation is required for IPv6 addresses.

Note that this function assumes that the input string is a well-formed IP address - it does not attempt to handle cases where the input string is malformed or otherwise invalid.