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Parse and stringify BCP 47 language tags.

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What is this?

This is a package that can parse BCP 47 language tags to an object representing them, and serialize those objects back into language tags. It supports a forgiving mode to handle incorrect BCP 47 tags and can emit warnings about problems in incorrect tags.

When should I use this?

You can use this package if you need to access the data stored in BCP 47 language tags. You can also use this package if you want to check (lint) or manipulate tags.

Install

This package is ESM only. In Node.js (version 14.14+, 16.0+), install with npm:

npm install bcp-47

In Deno with esm.sh:

import * as bcp47 from 'https://esm.sh/bcp-47@2'

In browsers with esm.sh:

<script type="module">
  import * as bcp47 from 'https://esm.sh/bcp-47@2?bundle'
</script>

Use

import {parse, stringify} from 'bcp-47'

const schema = parse('hy-Latn-IT-arevela')

console.log(schema)
console.log(stringify(schema))

Yields:

{ language: 'hy',
  extendedLanguageSubtags: [],
  script: 'Latn',
  region: 'IT',
  variants: ['arevela'],
  extensions: [],
  privateuse: [],
  irregular: null,
  regular: null }
'hy-Latn-IT-arevela'

API

This package exports the identifiers parse and stringify. There is no default export.

parse(tag[, options])

Parse a BCP 47 tag into a language schema.

šŸ‘‰ Note: the algorithm is case insensitive.

options.normalize

Whether to normalize legacy tags when possible (boolean, default: true). For example, i-klingon does not match the BCP 47 language algorithm but is considered valid by BCP 47 nonetheless. It is suggested to use tlh instead (the ISO 639-3 code for Klingon). When normalize is true, passing i-klingon or other deprecated tags, is handled as if their suggested valid tag was given instead.

options.forgiving

By default, when an error is encountered, an empty object is returned. When in forgiving mode, all found values up to the point of the error are included (boolean, default: false). So, for example, where by default en-GB-abcdefghi an empty object is returned (as the language variant is too long), in forgiving mode the language of schema is populated with en and the region is populated with GB.

options.warning

When given, warning is called when an error is encountered (Function).

Returns

Parsed BCP 47 language tag (Schema).

Throws

When tag is null or undefined.

stringify(schema)

Compile a schema to a BCP 47 language tag.

Returns

BCP 47 language tag (string).

Schema

A schema represents a language tag. A schema is deemed empty when it has neither language, irregular, regular, nor privateuse (where an empty privateuse array is handled as no privateuse as well).

schema.language

Two or three character ISO 639 language code, four character reserved language code, or 5 to 8 (inclusive) characters registered language subtag (string). For example, en (English) or cmn (Mandarin Chinese).

schema.extendedLanguageSubtags

Selected three-character ISO 639 codes (Array<string>), such as yue in zh-yue-HK (Chinese, Cantonese, as used in Hong Kong SAR).

schema.script

Four character ISO 15924 script code (string), such as Latn in hy-Latn-IT-arevela (Eastern Armenian written in Latin script, as used in Italy).

schema.region

Two alphabetical character ISO 3166-1 code or three digit UN M49 code (string). For example, CN in cmn-Hans-CN (Mandarin Chinese, Simplified script, as used in China) or 419 in es-419 (Spanish as used in Latin America and the Caribbean).

schema.variants

5 to 8 (inclusive) character language variants (Array<string>), such as rozaj and biske in sl-rozaj-biske (San Giorgio dialect of Resian dialect of Slovenian).

schema.extensions

List of extensions (Array<Object>), each an object containing a one character singleton, and a list of extensions (string). singleton cannot be x (case insensitive) and extensions must be between two and eight (inclusive) characters. For example, an extension would be u-co-phonebk in de-DE-u-co-phonebk (German, as used in Germany, using German phonebook sort order), where u is the singleton and co and phonebk are its extensions.

schema.privateuse

List of private-use subtags (Array<string>), where each subtag must be between one and eight (inclusive) characters.

schema.regular

One of the regular tags (string): tags that are seen as something different by the algorithm. Valid values are:

schema.irregular

One of the irregular tags (string): tags that are seen as invalid by the algorithm). Valid values are:

function warning(reason, code, offset)

Called when an error occurs.

Parameters
Warnings
codereason
1Too long variant, expected at most 8 characters
2Too long extension, expected at most 8 characters
3Too many extended language subtags, expected at most 3 subtags
4Empty extension, extensions must have at least 2 characters of content
5Too long private-use area, expected at most 8 characters
6Found superfluous content after tag

Types

This package is fully typed with TypeScript. It exports the additional types Schema, Extension, Warning, and Options.

Compatibility

This package is at least compatible with all maintained versions of Node.js. As of now, that is Node.js 14.14+ and 16.0+. It also works in Deno and modern browsers.

Security

This package is safe.

Related

Contribute

Yes please! See How to Contribute to Open Source.

License

MIT Ā© Titus Wormer

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