Punycode converter

A Punycode converter that fully complies with RFC 3492 and RFC 5891.

Punycode is a representation of Unicode with the limited ASCII character subset used for Internet hostnames. Using Punycode, host names containing Unicode characters are transcoded to a subset of ASCII consisting of letters, digits, and hyphens, which is called the letter–digit–hyphen (LDH) subset. For example, München (German name for Munich) is encoded as Mnchen-3ya.

Usage

Tip: Run the example below by typing this in your terminal (requires Deno):

deno run \
  --allow-net --allow-run --allow-env --allow-read \
  https://deno.land/x/mdrb@2.0.0/mod.ts \
  --dax=false --mode=isolated \
  https://raw.githubusercontent.com/doga/punycode/main/README.md

Example: Convert Unicode DNS names to punycode and back.

description = '''
Running this example is safe, it will not read or write anything to your filesystem.
'''

import { punycode } from 'https://esm.sh/gh/doga/punycode@1.0.0/mod.mjs';

const unicodeDnsNames = [
    'mañana.rocks', '☃-⌘.design', 'джpумлатест.bрфa', 'hello.codes',
    '0.0.0.0', '::1'
 ];

unicodeDnsNames.forEach(name => {
    console.info(
`${name}
  encoded: ${punycode.toASCII(name)}
  decoded: ${punycode.toUnicode(punycode.toASCII(name))}\n`);
});

Sample output for the code above:

mañana.rocks
  encoded: xn--maana-pta.rocks
  decoded: mañana.rocks

☃-⌘.design
  encoded: xn----dqo34k.design
  decoded: ☃-⌘.design

джpумлатест.bрфa
  encoded: xn--p-8sbkgc5ag7bhce.xn--ba-lmcq
  decoded: джpумлатест.bрфa

hello.codes
  encoded: hello.codes
  decoded: hello.codes

0.0.0.0
  encoded: 0.0.0.0
  decoded: 0.0.0.0

::1
  encoded: ::1
  decoded: ::1

The full API

punycode.decode(string)

Converts a Punycode string of ASCII symbols to a string of Unicode symbols.

// decode domain name parts
punycode.decode('maana-pta'); // 'mañana'
punycode.decode('--dqo34k'); // '☃-⌘'

punycode.encode(string)

Converts a string of Unicode symbols to a Punycode string of ASCII symbols.

// encode domain name parts
punycode.encode('mañana'); // 'maana-pta'
punycode.encode('☃-⌘'); // '--dqo34k'

punycode.toUnicode(input)

Converts a Punycode string representing a domain name or an email address to Unicode. Only the Punycoded parts of the input will be converted, i.e. it doesn’t matter if you call it on a string that has already been converted to Unicode.

// decode domain names
punycode.toUnicode('xn--maana-pta.com');
// → 'mañana.com'
punycode.toUnicode('xn----dqo34k.com');
// → '☃-⌘.com'

// decode email addresses
punycode.toUnicode('джумла@xn--p-8sbkgc5ag7bhce.xn--ba-lmcq');
// → 'джумла@джpумлатест.bрфa'

punycode.toASCII(input)

Converts a lowercased Unicode string representing a domain name or an email address to Punycode. Only the non-ASCII parts of the input will be converted, i.e. it doesn’t matter if you call it with a domain that’s already in ASCII.

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

// encode email addresses
punycode.toASCII('джумла@джpумлатест.bрфa');
// → 'джумла@xn--p-8sbkgc5ag7bhce.xn--ba-lmcq'

punycode.ucs2

punycode.ucs2.decode(string)

Creates an array containing the numeric code point values of each Unicode symbol in the string. While JavaScript uses UCS-2 internally, this function will convert a pair of surrogate halves (each of which UCS-2 exposes as separate characters) into a single code point, matching UTF-16.

punycode.ucs2.decode('abc');
// → [0x61, 0x62, 0x63]
// surrogate pair for U+1D306 TETRAGRAM FOR CENTRE:
punycode.ucs2.decode('\uD834\uDF06');
// → [0x1D306]

punycode.ucs2.encode(codePoints)

Creates a string based on an array of numeric code point values.

punycode.ucs2.encode([0x61, 0x62, 0x63]);
// → 'abc'
punycode.ucs2.encode([0x1D306]);
// → '\uD834\uDF06'

punycode.version

A string representing the current Punycode.js version number.

License

This software is released under the Apache 2.0 license.

∎