isIP.js

// https://github.com/validatorjs/validator.js/blob/master/src/lib/isIP.js

/**
11.3.  Examples

   The following addresses

             fe80::1234 (on the 1st link of the node)
             ff02::5678 (on the 5th link of the node)
             ff08::9abc (on the 10th organization of the node)

   would be represented as follows:

             fe80::1234%1
             ff02::5678%5
             ff08::9abc%10

   (Here we assume a natural translation from a zone index to the
   <zone_id> part, where the Nth zone of any scope is translated into
   "N".)

   If we use interface names as <zone_id>, those addresses could also be
   represented as follows:

            fe80::1234%ne0
            ff02::5678%pvc1.3
            ff08::9abc%interface10

   where the interface "ne0" belongs to the 1st link, "pvc1.3" belongs
   to the 5th link, and "interface10" belongs to the 10th organization.
 * * */
const IPv4SegmentFormat =
  "(?:[0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])";
const IPv4AddressFormat = `(${IPv4SegmentFormat}[.]){3}${IPv4SegmentFormat}`;
const IPv4AddressRegExp = new RegExp(`^${IPv4AddressFormat}$`);

const IPv6SegmentFormat = "(?:[0-9a-fA-F]{1,4})";
const IPv6AddressRegExp = new RegExp(
  "^(" +
    `(?:${IPv6SegmentFormat}:){7}(?:${IPv6SegmentFormat}|:)|` +
    `(?:${IPv6SegmentFormat}:){6}(?:${IPv4AddressFormat}|:${IPv6SegmentFormat}|:)|` +
    `(?:${IPv6SegmentFormat}:){5}(?::${IPv4AddressFormat}|(:${IPv6SegmentFormat}){1,2}|:)|` +
    `(?:${IPv6SegmentFormat}:){4}(?:(:${IPv6SegmentFormat}){0,1}:${IPv4AddressFormat}|(:${IPv6SegmentFormat}){1,3}|:)|` +
    `(?:${IPv6SegmentFormat}:){3}(?:(:${IPv6SegmentFormat}){0,2}:${IPv4AddressFormat}|(:${IPv6SegmentFormat}){1,4}|:)|` +
    `(?:${IPv6SegmentFormat}:){2}(?:(:${IPv6SegmentFormat}){0,3}:${IPv4AddressFormat}|(:${IPv6SegmentFormat}){1,5}|:)|` +
    `(?:${IPv6SegmentFormat}:){1}(?:(:${IPv6SegmentFormat}){0,4}:${IPv4AddressFormat}|(:${IPv6SegmentFormat}){1,6}|:)|` +
    `(?::((?::${IPv6SegmentFormat}){0,5}:${IPv4AddressFormat}|(?::${IPv6SegmentFormat}){1,7}|:))` +
    ")(%[0-9a-zA-Z-.:]{1,})?$"
);

function isIP_(str, version = "") {
  assertString_(str);
  version = String(version);
  if (!version) {
    return isIP_(str, 4) || isIP_(str, 6);
  }
  if (version === "4") {
    if (!IPv4AddressRegExp.test(str)) {
      return false;
    }
    const parts = str.split(".").sort((a, b) => a - b);
    return parts[3] <= 255;
  }
  if (version === "6") {
    return !!IPv6AddressRegExp.test(str);
  }
  return false;
}