function toASCII

The punycode.toASCII() method converts a Unicode string representing an Internationalized Domain Name to Punycode. Only the non-ASCII parts of the domain name will be converted. Calling punycode.toASCII() on a string that already only contains ASCII characters will have no effect.

// encode domain names
punycode.toASCII('mañana.com');  // 'xn--maana-pta.com'
punycode.toASCII('☃-⌘.com');   // 'xn----dqo34k.com'
punycode.toASCII('example.com'); // 'example.com'