@dojo/i18n

An internationalization library that provides locale-specific message loading, and support for locale-specific message, date, and number formatting.

• Usage
• Features
  • Message Bundle Loading
  • Determining the Current Locale
  • Changing the Root Locale and Observing Locale Changes
  • Loading CLDR data
  • Message Formatting
  • Date and number formatting
• How do I contribute?
  • Installation
  • Testing
• Licensing information

Usage

To use @dojo/i18n, install the package along with its required peer dependencies:

npm install @dojo/i18n

# peer dependencies
npm install @dojo/core
npm install @dojo/has
npm install @dojo/shim

With TypeScript or ES6 modules, you would generally want to just import the @dojo/i18n/i18n module:

import i18n, { Messages } from '@dojo/i18n/i18n';
import messageBundle from 'path/to/bundle';

i18n(messageBundle, 'fr').then((messages: Messages) => {
	// locale-specific messages ready to use...
});

Features

The examples below are provided in TypeScript syntax. The package does work under JavaScript, but for clarity, the examples will only include one syntax.

Message Bundle Loading

@dojo/i18n provides a means for loading locale-specific messages and updating those messages when the locale changes. Each bundle has a default module that is imported like any other TypeScript module. Locale-specific messages are then loaded via the i18n method. Every default bundle MUST provide a messages map containing default messages, and an optional locales object that maps supported locales to functions that load their respective translations. Further, each default bundle is assigned a unique id property that is used internally to manage caching and handle interoperability with Globalize.js (see below). While it is possible to include an id with your message bundles, doing so is neither necessary nor recommended.

import fr from './fr/main';

export default {
	locales: {
		// Locale providers can load translations lazily...
		ar: () => import('./ar/main'),
		'ar-JO': () => import('./ar-JO/main'),

		// ... or locale providers can return translations directly.
		fr: () => fr
	},
	messages: {
		hello: 'Hello',
		goodbye: 'Goodbye'
	}
};

The messages object contains default messages for all keys used through the bundle. These messages are used as fallbacks for any messages not included in locale-specific bundles. Further, the locales map uses functions to load translations, providing an extra layer of flexibility in determining how translations are included. The locale bundles expose their messages on their default exports (in this case, nls/fr/main):

const messages = {
	hello: 'Bonjour',
	goodbye: 'Au revoir'
};
export default messages;

Once the default bundle is in place, any locale-specific messages are loaded by passing the default bundle to the i18n function. Using the previous example as the default bundle, any locale-specific messages are loaded as follows:

import i18n, { Messages } from '@dojo/i18n/main';
import bundle from 'nls/main';

i18n(bundle, 'fr').then(function (messages: Messages) {
	console.log(messages.hello); // "Bonjour"
	console.log(messages.goodbye); // "Au revoir"
});

If an unsupported locale is passed to i18n, then the default messages are returned. Further, any messages not provided by the locale-specific bundle will also fall back to their defaults. As such, the default bundle should contain all message keys used by any of the locale-specific bundles.

Alternatively, locale messages can be manually loaded by passing them to setLocaleMessages. This is useful for pre-caching locale-specific messages so that an additional HTTP request is not sent to load them. Locale-specific messages are merged with the default messages, so partial message bundles are acceptable:

import i18n, { setLocaleMessages } from '@dojo/i18n/i18n';
import bundle from 'nls/main';

const partialMessages = { hello: 'Ahoj' };
setLocaleMessages(bundle, partialMessages, 'cz');

i18n(bundle, 'cz').then((messages) => {
	console.log(messages.hello); // "Ahoj"
	console.log(messages.goodbye); // "Goodbye" (defaults are used when not overridden)
});

Once locale dictionaries for a bundle have been loaded, they are cached and can be accessed synchronously via getCachedMessages:

import { getCachedMessages } from '@dojo/i18n/i18n';
import bundle from 'nls/main';

const messages = getCachedMessages(bundle, 'fr');
console.log(messages.hello); // "Bonjour"
console.log(messages.goodbye); // "Au revoir"

getCachedMessages will look up the bundle's supported locales to determine whether the default messages should be returned. Locales are also normalized to their most specific messages. For example, if the 'fr' locale is supported, but 'fr-CA' is not, getCachedMessages will return the messages for the 'fr' locale:

import { getCachedMessages } from '@dojo/i18n/i18n';
import bundle from 'nls/main';

const frenchMessages = getCachedMessages(bundle, 'fr-CA');
console.log(frenchMessages.hello); // "Bonjour"
console.log(frenchMessages.goodbye); // "Au revoir"

const madeUpLocaleMessages = getCachedMessages(bundle, 'made-up-locale');
console.log(madeUpLocaleMessages.hello); // "Hello"
console.log(madeUpLocaleMessages.goodbye); // "Goodbye"

If need be, bundle caches can be cleared with invalidate. If called with a bundle, only the messages for that particular bundle are removed from the cache. Otherwise, all messages are cleared:

import i18n, { getCachedMessages, invalidate } from '@dojo/i18n/main';
import bundle from 'nls/main';

i18n(bundle, 'ar').then(() => {
	invalidate(bundle);
	console.log(getCachedMessages(bundle, 'ar')); // undefined
});

Determining the Current Locale

The current locale can be accessed via the read-only property i18n.locale, which will always be either the locale set via switchLocale (see below) or the systemLocale. systemLocale is always set to the user's default locale.

Changing the Root Locale and Observing Locale Changes

The switchLocale method changes the root locale and notifies all consumers registered with observeLocale, which accepts a function that receives the new locale string as its sole argument. For example, suppose the system locale is en-GB:

import i18n, { observeLocale, switchLocale, systemLocale } from '@dojo/i18n/i18n';
import bundle from 'nls/bundle';

// Register an event listener
observeLocale((locale: string) => {
	// handle locale change...
});

// Change the locale to German. The registered observer's callback will be called
// with the new locale.
switchLocale('de');

// The locale is again switched to German, but since the current root locale is
// already German, registered observers will not be notified.
switchLocale('de');

console.log(i18n.locale); // 'de'
console.log(systemLocale); // 'en-GB' (the system locale does not change with the root locale)

Loading CLDR data

Given the very large size of the Unicode CLDR data, it is not included as a dependency of @dojo/i18n. For applications that use @dojo/i18n only for selecting unformatted, locale-specific messages, this is not a concern. However, if using the ICU-formatted messages or any of the other formatters provided by @dojo/i18n (see below), applications must explicitly load any required CLDR data via the loadCldrData method exported by @dojo/i18n/cldr/load. loadCldrData accepts an object of CLDR data. All CLDR data MUST match the format used by the Unicode CLDR JSON files. Supplemental data MUST be nested within a top-level supplemental object, and locale-specific data MUST be nested under locale objects within a top-level main object:

import loadCldrData from '@dojo/i18n/cldr/load';

loadCldrData({
	"supplemental": {
		"likelySubtags": { ... }
	},
	"main": {
		"en": {
			"numbers": { ... }
		}
	}
});

@dojo/i18n requires the following CLDR data:

For ICU message formatting:

• supplemental/likelySubtags
• supplemental/plurals

For date/time formatting:

• main/{locale}/ca-gregorian
• main/{locale}/dateFields
• main/{locale}/numbers
• main/{locale}/timeZoneNames
• supplemental/likelySubtags
• supplemental/numberingSystems
• supplemental/ordinals
• supplemental/plurals
• supplemental/timeData
• supplemental/weekData

For number/currency formatting:

• main/{locale}/currencies
• main/{locale}/numbers
• supplemental/currencyData
• supplemental/likelySubtags
• supplemental/numberingSystems
• supplemental/ordinals
• supplemental/plurals

For unit formatting:

• main/{locale}/numbers
• main/{locale}/units
• supplemental/likelySubtags
• supplemental/numberingSystems
• supplemental/ordinals
• supplemental/plurals

Message Formatting

The i18n module exposes two methods that handle message formatting: 1) formatMessage, which directly returns a formatted message based on its inputs, and 2) getMessageFormatter, which returns a method dedicated to formatting a single message. Both of these methods operate on bundle objects, which must first be registered with the i18n ecosystem by passing them to the i18n function (see below).

@dojo/i18n supports the ICU message format (see below), but that requires CLDR data and is not something that every application requires. As such, if the supplemental/likeSubtags and supplemental/plurals data are not loaded, then both formatMessage and getMessageFormatter will perform simple token replacement. For example, given the guestInfo message {host} invites {guest} to the party., an object with host and guest properties can be provided to a formatter without the need to load CLDR data:

import i18n, { formatMessage, getMessageFormatter } from '@dojo/i18n/i18n';
import bundle from 'nls/main';

i18n(bundle, 'en').then(() => {
	const formatter = getMessageFormatter(bundle, 'guestInfo', 'en');
	let message = formatter({
		host: 'Margaret Mead',
		guest: 'Laura Nader'
	});
	console.log(message); // "Margaret Mead invites Laura Nader to the party."

	// Note that `formatMessage` is essentially a convenience wrapper around `getMessageFormatter`.
	message = formatMessage(bundle, 'guestInfo', {
		host: 'Marshall Sahlins',
		gender: 'male',
		guest: 'Bronisław Malinowski'
	}, 'en');
	console.log(message); // "Marshall Sahlins invites Bronisław Malinowski to the party."
});

ICU Message Formatting

Note: This feature requires CLDR data (see above).

@dojo/i18n relies on Globalize.js for ICU message formatting, and as such all of the features offered by Globalize.js are available through @dojo/i18n.

As an example, suppose there is a locale bundle with a guestInfo message:

const messages = {
	guestInfo: `{gender, select,
		female {
			{guestCount, plural, offset:1
			=0 {{host} does not give a party.}
			=1 {{host} invites {guest} to her party.}
			=2 {{host} invites {guest} and one other person to her party.}
			other {{host} invites {guest} and # other people to her party.}}}
		male {
			{guestCount, plural, offset:1
			=0 {{host} does not give a party.}
			=1 {{host} invites {guest} to his party.}
			=2 {{host} invites {guest} and one other person to his party.}
			other {{host} invites {guest} and # other people to his party.}}}
		other {
			{guestCount, plural, offset:1
			=0 {{host} does not give a party.}
			=1 {{host} invites {guest} to their party.}
			=2 {{host} invites {guest} and one other person to their party.}
			other {{host} invites {guest} and # other people to their party.}}}}`
};
export default messages;

The above message can be converted directly with formatMessage, or getMessageFormatter can be used to generate a function that can be used over and over with different options. Note that the formatters created and used by both methods are cached, so there is no performance penalty from compiling the same message multiple times.

Since the Globalize.js formatting methods use message paths rather than the message strings themselves, the @dojo/i18n methods also require that the bundle itself be provided, so its unique identifier can be resolved to a message path within the Globalize.js ecosystem. If an optional locale is provided, then the corresponding locale-specific message will be used. Otherwise, the current locale is assumed.

import i18n, { formatMessage, getMessageFormatter } from '@dojo/i18n/i18n';
import bundle from 'nls/main';

// 1. Load the messages for the locale.
i18n(bundle, 'en').then(() => {
	const message = formatMessage(bundle, 'guestInfo', {
		host: 'Margaret Mead',
		gender: 'female',
		guest: 'Laura Nader',
		guestCount: 20
	}, 'en');
	console.log(message); // "Margaret Mead invites Laura Nader and 19 other people to her party."

	const formatter = getMessageFormatter(bundle, 'guestInfo', 'en');
	console.log(formatter({
		host: 'Margaret Mead',
		gender: 'female',
		guest: 'Laura Nader',
		guestCount: 20
	})); // "Margaret Mead invites Laura Nader and 19 other people to her party."

	console.log(formatter({
		host: 'Marshall Sahlins',
		gender: 'male',
		guest: 'Bronisław Malinowski'
	})); // "Marshall Sahlins invites Bronisław Malinowski to his party."
});

Date and number formatting.

Note: This feature requires CLDR data (see above).

As with the message formatting capabilities, @dojo/i18n relies on Globalize.js to provide locale-specific formatting for dates, times, currencies, numbers, and units. The formatters themselves are essentially light wrappers around their Globalize.js counterparts, which helps maintain consistency with the Dojo 2 ecosystem and prevents the need to work with the Globalize object directly. Unlike the message formatters, the date, number, and unit formatters are not cached, as they have a more complex set of options. As such, executing the various "get formatter" methods multiple times with the same inputs does not return the exact same function object.

@dojo/i18n groups the various formatters accordingly: date and time formatters (@dojo/i18n/date); number, currency, and pluralization formatters (@dojo/i18n/number); and unit formatters (@dojo/i18n/unit). Each method corresponds to a Globalize.js method (see below), and each method follows the same basic format: the last argument is an optional locale, and the penultimate argument is the method options. If specifying a locale but no options, pass null as the options argument. If no locale is provided, then the current (i18n.locale) is assumed.

import { formatDate, getDateFormatter, formatRelativeTime } from '@dojo/i18n/date';
import { formatCurrency, getCurrencyFormatter } from '@dojo/i18n/number';
import { formatUnit, getUnitFormatter } from '@dojo/i18n/unit';

const date = new Date(1815, 11, 10, 11, 27);

// Assume the current locale is "en"
const enDateFormatter = getDateFormatter({ datetime: 'medium' });
enDateFormatter(date); // Dec 10, 1815, 11:27:00 AM
formatDate(date, { date: 'short' }); // 12/10/15

const frDateFormatter = getDateFormatter({ datetime: 'medium' }, 'fr');
frDateFormatter(date); // 10 déc. 1815 à 11:27:00
formatDate(date, { date: 'short' }, 'fr'); // 10/12/1815

formatRelativeTime(-1, 'week'); // "last week"
formatRelativeTime(-1, 'week', { form: 'short' }); // "last wk."
formatRelativeTime(-3, 'week', null, 'fr'); // "il y a 3 semaines"
formatRelativeTime(-3, 'week', { form: 'short' }, 'fr'); // "il y a 3 sem."

const enCurrencyFormatter = getCurrencyFormatter('USD', { style: 'code' });
enCurrencyFormatter(1234.56); // "1,234.56 USD"
formatCurrency(12345.56, 'USD', { style: 'code' }); // "1,234.56 USD"

const frCurrencyFormatter = getCurrencyFormatter('EUR', { style: 'code' }, 'fr');
frCurrencyFormatter(1234.56); // "1 234,56 EUR"
formatCurrency(12345.56, 'EUR', { style: 'code' }, 'fr'); // "1 234,56 EUR"

const enUnitFormatter = getUnitFormatter('feet', { form: 'narrow' });
enUnitFormatter(5280); // 5,280′
formatUnit(5280, 'feet', { form: 'narrow' }); // 5,280′

const frUnitFormatter = getUnitFormatter('meter', null, 'fr');
frUnitFormatter(1000); // 1 000 mètres'
formatUnit(1000, 'meter', null, 'fr); // 1 000 mètres'

@dojo/i18n/date methods:

• formatDate => Globalize.formatDate
• formatRelativeTime => Globalize.formatRelativeTime
• getDateFormatter => Globalize.dateFormatter
• getDateParser => Globalize.dateParser
• getRelativeTimeFormatter => Globalize.relativeTimeFormatter
• parseDate => Globalize.parseDate

@dojo/i18n/number methods:

• formatCurrency => Globalize.formatCurrency
• formatNumber => Globalize.formatNumber
• getCurrencyFormatter => Globalize.currencyFormatter
• getNumberFormatter => Globalize.numberFormatter
• getNumberParser => Globalize.numberParser
• getPluralGenerator => Globalize.pluralGenerator
• parseNumber => Globalize.parseNumber
• pluralize => Globalize.plural

@dojo/i18n/unit methods:

• formatUnit => Globalize.formatUnit
• getUnitFormatter => Globalize.unitFormatter

How do I contribute?

We appreciate your interest! Please see the Guidelines Repository for the Contributing Guidelines.

Code Style

This repository uses prettier for code styling rules and formatting. A pre-commit hook is installed automatically and configured to run prettier against all staged files as per the configuration in the project's package.json.

An additional npm script to run prettier (with write set to true) against all src and test project files is available by running:

npm run prettier

Installation

To start working with this package, clone the repository and run npm install.

In order to build the project run grunt dev or grunt dist.

Testing

Test cases MUST be written using Intern using the Object test interface and Assert assertion interface.

90% branch coverage MUST be provided for all code submitted to this repository, as reported by istanbul’s combined coverage results for all supported platforms.

Licensing information

• Globalize.js (MIT)

© 2018 JS Foundation. New BSD license.