bcp47

library0.1.0jsnpmunverified

The `bcp47` package provides a parser for BCP 47 language tags, a critical standard used in internationalization (i18n) for identifying human languages. The current stable version is `1.2.0`, with a rapid succession of recent releases in April 2026, indicating active development or a recent relaunch. This library's core function is to parse a BCP 47 tag and return a structured object containing all extracted components, or `null` if the tag is syntactically invalid, which acts as an implicit validation mechanism. Its key differentiator lies in its focused adherence to the BCP 47 specification, offering a lightweight and precise tool for tasks like content negotiation, managing localization resources, or configuring user interface languages. Unlike broader i18n frameworks, `bcp47` provides a dedicated, minimalist solution for this specific parsing requirement.

serialization communication

npm install bcp47

github ↗package ↗

INSTALL

IMPORT

SIG · BCP47

bcp47

serializationjavascriptv0.1.0

Install

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Import

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Disk

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Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

parse

✓ import { parse } from 'bcp47';

✗ import bcp47 from 'bcp47'; bcp47.parse(...);

The `parse` function is a named export for ESM. It does not export a default.

stringify

✓ import { stringify } from 'bcp47';

✗ const stringify = require('bcp47').stringify;

The `stringify` function is also a named export, complementing `parse` for reconstructing tags.

parse (CommonJS)

✓ const { parse } = require('bcp47');

✗ const bcp47 = require('bcp47'); const result = bcp47.parse('en-US');

CommonJS users should prefer destructuring for named exports like `parse`.

Demonstrates parsing valid and invalid BCP 47 language tags, showing the structured output and the `null` return for invalid input. Also includes stringification.

import { parse, stringify } from 'bcp47'; // Example 1: Parsing a valid language tag const tag1 = 'en-US-u-attr-value'; const parsedTag1 = parse(tag1); console.log('Parsed Tag 1:', parsedTag1); // Expected output: { language: 'en', extlangs: [], script: null, region: 'US', variants: [], extensions: [{ singleton: 'u', privateuse: 'attr-value' }], privateuse: null } // Example 2: Parsing an invalid language tag const tag2 = 'invalid-tag-$$'; const parsedTag2 = parse(tag2); console.log('Parsed Tag 2 (invalid):', parsedTag2); // Expected output: null // Example 3: Parsing a tag with script and variant const tag3 = 'zh-Hans-SG-pinyin'; const parsedTag3 = parse(tag3); console.log('Parsed Tag 3:', parsedTag3); // Example 4: Stringifying a parsed object back to a tag if (parsedTag3) { const rebuiltTag = stringify(parsedTag3); console.log('Rebuilt Tag 3:', rebuiltTag); }

Debug

Known issues

gotchaThe `parse` function returns `null` for any input that does not conform to the BCP 47 specification. This includes malformed tags, empty strings, or non-string inputs. Developers must explicitly check for `null` to avoid runtime errors when accessing properties of the parsed object.

fix

Always check the return value of `parse()`: `const result = parse(tag); if (result) { /* use result */ } else { /* handle invalid tag */ }`

affects: >=1.0.0

gotchaThe package specifies `"engines": { "node": ">=0.10" }`, indicating compatibility with extremely old Node.js versions. While this might suggest broad compatibility, modern applications should be aware that the code may not leverage contemporary JavaScript features or optimizations. However, given recent releases (April 2026), it's more likely a legacy `package.json` entry or the project has been significantly updated recently.

fix

No direct fix for usage, but be mindful of the potential discrepancy between listed engine requirements and actual modern development practices. Test thoroughly on your target Node.js version.

affects: >=1.0.0

Errors

Common errors & fixes

TypeError: Cannot read properties of null (reading 'language')

Attempting to access properties of the object returned by `parse()` without checking if the tag was valid, leading to an attempt to access properties on `null`.

fix

Ensure the result of `parse()` is not `null` before attempting to access its properties. For example: `const parsed = parse(tag); if (parsed) { console.log(parsed.language); } else { console.error('Invalid BCP 47 tag'); }`

TypeError: tag.toLowerCase is not a function

Passing a non-string value (e.g., `null`, `undefined`, a number, or an object) to the `parse()` function, which expects a string.

fix

Always ensure the input to `parse()` is a string. Validate the input type before calling `parse()`: `if (typeof tag === 'string') { parse(tag); } else { /* handle invalid input type */ }`

Upgrade

Version history

0.1.0latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

41 hits · last 30 days

node

OpenAI (training)

Resources

githubhttps://github.com/gagle/node-bcp47 ↗

packagehttps://www.npmjs.com/package/bcp47 ↗