I18n and L10n in AngularJS

What is i18n and l10n?

Internationalization, abbreviated i18n, is the process of developing products in such a way that they can be localized for languages and cultures easily. Localization, abbreviated l10n, is the process of adapting applications and text to enable their usability in a particular cultural or linguistic market. For application developers, internationalizing an application means abstracting all of the strings and other locale-specific bits (such as date or currency formats) out of the application. Localizing an application means providing translations and localized formats for the abstracted bits.

What level of support for i18n/l10n is currently in Angular?

Currently, Angular supports i18n/l10n for datetime, number and currency filters.

Additionally, Angular supports localizable pluralization support provided by the ngPluralize directive.

All localizable Angular components depend on locale-specific rule sets managed by the $locale service.

For readers who want to jump straight into examples, we have a few web pages that showcase how to use Angular filters with various locale rule sets. You can find these examples either on Github or in the i18n/e2e folder of Angular development package.

What is a locale id?

A locale is a specific geographical, political, or cultural region. The most commonly used locale ID consists of two parts: language code and country code. For example, en-US, en-AU, zh-CN are all valid locale IDs that have both language codes and country codes. Because specifying a country code in locale ID is optional, locale IDs such as en, zh, and sk are also valid. See the ICU website for more information about using locale IDs.

Supported locales in Angular Angular separates number and datetime format rule sets into different files, each file for a particular locale. You can find a list of currently supported locales here

Providing locale rules to Angular

There are two approaches to providing locale rules to Angular:

1. Pre-bundled rule sets

You can pre-bundle the desired locale file with Angular by concatenating the content of the locale-specific file to the end of angular.js or angular.min.js file.

For example on *nix, to create an angular.js file that contains localization rules for german locale, you can do the following:

cat angular.js i18n/angular-locale_de-de.js > angular_de-de.js

When the application containing angular_de-de.js script instead of the generic angular.js script starts, Angular is automatically pre-configured with localization rules for the german locale.

2. Including locale js script in index.html page

You can also include the locale specific js file in the index.html page. For example, if one client requires German locale, you would serve index_de-de.html which will look something like this:

<html ng-app>
 <head>
….
   <script src="angular.js"></script>
   <script src="i18n/angular-locale_de-de.js"></script>
….
 </head>
</html>

Comparison of the two approaches Both approaches described above requires you to prepare different index.html pages or js files for each locale that your app may be localized into. You also need to configure your server to serve the correct file that correspond to the desired locale.

However, the second approach (Including locale js script in index.html page) is likely to be slower because an extra script needs to be loaded.

"Gotchas"

Currency symbol "gotcha"

Angular's currency filter allows you to use the default currency symbol from the locale service, or you can provide the filter with a custom currency symbol. If your app will be used only in one locale, it is fine to rely on the default currency symbol. However, if you anticipate that viewers in other locales might use your app, you should provide your own currency symbol to make sure the actual value is understood.

For example, if you want to display account balance of 1000 dollars with the following binding containing currency filter: {{ 1000 | currency }}, and your app is currently in en-US locale. '$1000.00' will be shown. However, if someone in a different local (say, Japan) views your app, her browser will specify the locale as ja, and the balance of '¥1000.00' will be shown instead. This will really upset your client.

In this case, you need to override the default currency symbol by providing the currency filter with a currency symbol as a parameter when you configure the filter, for example, {{ 1000 | currency:"USD$"}}. This way, Angular will always show a balance of 'USD$1000' and disregard any locale changes.

Translation length "gotcha"

Keep in mind that translated strings/datetime formats can vary greatly in length. For example, June 3, 1977 will be translated to Spanish as 3 de junio de 1977. There are bound to be other more extreme cases. Hence, when internationalizing your apps, you need to apply CSS rules accordingly and do thorough testing to make sure UI components do not overlap.

Timezones

Keep in mind that Angular datetime filter uses the time zone settings of the browser. So the same application will show different time information depending on the time zone settings of the computer that the application is running on. Neither Javascript nor Angular currently supports displaying the date with a timezone specified by the developer.