is-localhost-ip

is-localhost-ip

Comprehensive and robust library to checks whether given host name or IPv4/IPv6 address belongs to the local machine

Main difference from other libraries here is comprehensiveness: we start from strict RegExp checks (for IP address first, and then for correctness to be a host name), then fallback to DNS resolver (so it works with something like john.dev remapped locally in hosts or with local resolver).

All this in just ~100 lines of code without external dependencies.

Installation

npm i is-localhost-ip
# or
yarn add is-localhost-ip

Example

const isLocalhost = require("is-localhost-ip");

(async () => {
  await isLocalhost("127.0.0.1"); // true
  await isLocalhost("::ffff:127.0.0.1"); // true
  await isLocalhost("192.168.0.12"); // true
  await isLocalhost("192.168.0.12", true); // true only if the local machine has an interface with that address
  await isLocalhost("184.55.123.2"); // false

  await isLocalhost("tino.local"); // true
  await isLocalhost("localhost"); // true
  await isLocalhost("microsoft.com"); // false
})();

Caveats

Doesn't work with internationalized (RFC 3492 or RFC 5891) domain names. If you need that please use wonderful Punycode.js to convert the string before passing to this library:

const isLocalhost = require("is-localhost-ip");
const punycode = require("punycode");

(async () => {
  await isLocalhost(punycode.toASCII("свобода.рф")); // false
  await isLocalhost(punycode.toASCII("私の.家")); // true
})();

License

is-localhost-ip is available under the MIT license.