toASCII = function toASCII(input) {
	return mapDomain(input, function (string) {
		return regexNonASCII.test(string) ? 'xn--' + encode(string) : string;
	});
}
Converts a Unicode string representing a domain name or an email address to
Punycode. Only the non-ASCII parts of the domain name will be converted,
i.e. it doesn't matter if you call it with a domain that's already in
ASCII.
@memberOf punycode
@param {String} input The domain name or email address to convert, as a
Unicode string.
@returns {String} The Punycode representation of the given domain name or
email address.