@postalsys/gettext is a JavaScript implementation of a substantial subset of GNU gettext, a powerful localization framework originally written in C. This library enables developers to internationalize their JavaScript applications by handling translations, plural forms, and contexts, closely mirroring the functionality of the original gettext.

If you're interested in parsing or compiling .mo/.po files for use with this library or elsewhere, consider using gettext-parser.

Features

Comprehensive Localization Support: Handles domains, contexts, plurals, and more.
File Format Compatibility: Supports .json, .mo, and .po files via gettext-parser.
Extensive Language Support: Includes plural forms for 136 languages.
Dynamic Configuration: Allows changing locale or domain at runtime.
Debugging Tools: Provides detailed error messages when the debug option is enabled.
Event Emission: Emits events for internal errors, such as missing translations.

Differences from GNU gettext

While @postalsys/gettext aims to closely emulate GNU gettext, there are notable differences:

No Category Support: Unlike GNU gettext, which supports categories like LC_MESSAGES, LC_NUMERIC, and LC_MONETARY, this library focuses solely on message localization, effectively always operating under the LC_MESSAGES category. For number formatting, currencies, dates, and other localization needs, consider using dedicated JavaScript libraries.
Manual Translation Loading: GNU gettext automatically reads translation files from the filesystem based on locale and category settings. In contrast, @postalsys/gettext requires developers to manually load and provide translations, accommodating both server-side and client-side environments.

Installation

Install the package via npm:

npm install @postalsys/gettext

Usage

Basic Example

const Gettext = require('@postalsys/gettext');
const swedishTranslations = require('./translations/sv-SE.json');

const gt = new Gettext();
gt.addTranslations('sv-SE', 'messages', swedishTranslations);
gt.setLocale('sv-SE');

console.log(gt.gettext('The world is a funny place'));
// Output: "Världen är en underlig plats"

Error Events

@postalsys/gettext emits an error event when it encounters issues such as missing translations. You can handle these events as follows:

// Set up your Gettext instance and add translations...

gt.on('error', error => {
    console.error('Translation error:', error.message);
});

gt.gettext('An unrecognized message');
// Logs: 'Translation error: No translation found for msgid "An unrecognized message"'

Recipes

Loading Translations from .mo or .po Files

@postalsys/gettext works seamlessly with translations parsed by gettext-parser. Here's how you can load translations from .po files:

const fs = require('fs');
const path = require('path');
const Gettext = require('@postalsys/gettext');
const { po } = require('gettext-parser');

// Directory where your translations are stored
const translationsDir = 'path/to/locales';
const locales = ['en', 'fi-FI', 'sv-SE'];
const domain = 'messages';

const gt = new Gettext();

locales.forEach(locale => {
    const filename = `${domain}.po`;
    const translationsFilePath = path.join(translationsDir, locale, filename);
    const translationsContent = fs.readFileSync(translationsFilePath);

    const parsedTranslations = po.parse(translationsContent);
    gt.addTranslations(locale, domain, parsedTranslations);
});

gt.setLocale('sv-SE');
console.log(gt.gettext('Hello'));
// Outputs the translated string in Swedish

API Reference

Gettext

Gettext
- new Gettext([options])
- .on(eventName, callback)
- .off(eventName, callback)
- .addTranslations(locale, domain, translations)
- .setLocale(locale)
- .setTextDomain(domain)
- .gettext(msgid) ⇒ String
- .dgettext(domain, msgid) ⇒ String
- .ngettext(msgid, msgidPlural, count) ⇒ String
- .dngettext(domain, msgid, msgidPlural, count) ⇒ String
- .pgettext(msgctxt, msgid) ⇒ String
- .dpgettext(domain, msgctxt, msgid) ⇒ String
- .npgettext(msgctxt, msgid, msgidPlural, count) ⇒ String
- .dnpgettext(domain, msgctxt, msgid, msgidPlural, count) ⇒ String

new Gettext([options])

Creates and returns a new Gettext instance.

Returns: Object - A Gettext instance
Params

[options]: Object - A set of options
- .sourceLocale: String - The locale that the source code and its texts are written in. Translations for this locale is not necessary.
- .debug: Boolean - Whether to output debug info into the console.

gettext.on(eventName, callback)

Adds an event listener.

Params

eventName: String - An event name
callback: function - An event handler function

gettext.off(eventName, callback)

Removes an event listener.

Params

eventName: String - An event name
callback: function - A previously registered event handler function

gettext.addTranslations(locale, domain, translations)

Stores a set of translations in the set of gettext catalogs.

Params

locale: String - A locale string
domain: String - A domain name
translations: Object - An object of gettext-parser JSON shape

Example

gt.addTranslations('sv-SE', 'messages', translationsObject)

gettext.setLocale(locale)

Sets the locale to get translated messages for.

Params

locale: String - A locale

Example

gt.setLocale('sv-SE')

gettext.setTextDomain(domain)

Sets the default gettext domain.

Params

domain: String - A gettext domain name

Example

gt.setTextDomain('domainname')