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AngularJS Localization done right.

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Table of Contents


A localization module for AngularJS complete with core service and accompanying filter, directives etc.

It is based on a number of angularjs localization modules already available out there on the web, and borrows heavily from the following list including but not limited to:

It was inspired by Jim Lavin's AngularJS Resource Localization Service who made an excellent first tutorial for his original version at Coding Smackdown TV which was later updated to include performance improvements seen here.

Main Points of Difference
  1. Simplified format of the translation file.
  2. Support for parameterized messages.
Major Improvements
  1. Parameters in the directive may be bound to $scope variables from the nearest parent controller.
  2. HTML element tag attributes can also be natively localized.
  3. Ability to configure a whole slew of things for more customizability to play nicely with your application.

Build Dependencies

  • node.js >= v0.10.x
  • npm
  • gulp npm install -g gulp
  • bower npm install -g bower

Dear Developer

$ npm install -d
$ npm test

In lieu of a formal style guide, please take good care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint and test your code using gulp.js. Please refer to this [document][commit-message-format] for a detailed explanation of git commit guidelines - source: AngularJS [commit-message-format]:

Getting Started

Quick Start

The easiest way to install the ngLocalize module is via Bower:

bower install angular-localization --save

Two other options are available:

You can then include angular-localization after its dependencies, angular and angular-cookies:

<script src="bower_components/angular/angular.js"></script>
<script src="bower_components/angular-cookies/angular-cookies.js"></script>
<script src="bower_components/angular-sanitize/angular-sanitize.js"></script>
<script src="bower_components/angular-localization/angular-localization.js"></script>

Wiring It Up

  1. Include the required libraries
  2. Ensure that you inject ngLocalize into your app by adding it to the dependency list.
angular.module('myApp', ['ngLocalize']);

Module Setup

All overridable configuration options are part of localeConf within the ngLocalize.Config module that comes bundled along with this plugin and works alongside ngLocalize

basePath @ languages

the folder off the root of your web app where the resource files are located (it can also be used as a relative path starting from the folder where your index.html file is located).

defaultLocale @ en-US

the locale that your app is initialized with for a new user

sharedDictionary @ common

commonly occuring words, phrases, strings etc. are stored in this file (it is used to check whether the service itself is ready or not as it is loaded during bootstrap)

fileExtension @ .lang.json

the extension for all resource files spanning across all languages

persistSelection @ true

whether to save the selected language to cookies for retrieval on later uses of the app


works in conjuntion with persistSelection and provides the cookie name for storage

observableAttrs @ \^data-(?!ng-|i18n)\

a regular expression which is used to match which custom data attibutes may be watched by the i18n directive for 2-way bindings to replace in a tokenized string

delimiter @ ::

the delimiter to be used when passing params along with the string token to the service, filter etc.

validTokens @ \^[\\w\\.-]+\\.[\\w\\s\\.-]+\\w(:.*)?$\

a regular expression which is used to match the names of the keys, so that they do not contain invalid characters. If you want to support an extended character set for the key names you need to change this.

angular.module('myApp', [
]).value('localeConf', {
    basePath: 'languages',
    defaultLocale: 'en-US',
    sharedDictionary: 'common',
    fileExtension: '.lang.json',
    persistSelection: true,
    cookieName: 'COOKIE_LOCALE_LANG',
    observableAttrs: new RegExp('^data-(?!ng-|i18n)'),
    delimiter: '::',
    validTokens: new RegExp('^[\\w\\.-]+\\.[\\w\\s\\.-]+\\w(:.*)?$')

NOTE: There is one caveat; if you want to override at least one particular option, then you must explicitly set any other options explicitly to their default values (shown above).

Availability of Events Fired

Publicly exposed events may be found as part of localeEvents situated within the ngLocalize.Events module that comes pre-loaded along with this plugin and is leveraged internally by the service.

  • localeEvents.resourceUpdates: when a new language file is pulled into memory
  • localeEvents.localeChanges: when the user chooses a different locale
angular.module('myApp', [
]).controller('myAppControl', ['$scope', 'localeEvents',
    function ($scope, localeEvents) {
        $scope.$on(localeEvents.resourceUpdates, function (data) {
            // Example data parameter for fr-FR common.lang.json bundle:
            // {
            //     locale: 'fr-FR',
            //     path: 'common',
            //     bundle: {
            //         "yes": "Oui",
            //         "no": "Aucun"
            //     }
            // }
        $scope.$on(localeEvents.localeChanges, function (event, data) {
            console.log('new locale chosen: ' + data);

NOTE: All of these are sent by $rootScope so that they may be accessible to all other $scopes within your app. Otherwise you could alternatively always choose to inject $rootScope and consume (ingest) the aforementioned events.

Declaration of New Languages

This plugin relies on the developer(s) to let it know of all languages currently part of the codebase. These languages must be defined as per the [Language Culture Name specification] ( It is broken up into two parts, both of which are located in the ngLocalize.InstalledLanguages modules separated out as localeSupported and localeFallbacks. The first is responsible for the list of languages currently supported as the name suggests while the latter takes care of fallbacks when a particular language is present but not for the region from which the app is being opened (e.g. en-GB). As a last resort, if none of these are valid and/or available, it will fallback to the defaultLocale configured as part of the options during initialization.

angular.module('myApp', [
.value('localeSupported', [
.value('localeFallbacks', {
    'en': 'en-US',
    'fr': 'fr-FR'

NOTE: Since the plugin does not rely on auto-discovery mechanisms of any kind, and none of the sort is planned for the future, it is possible to start creating language resource files before they must be fully integrated. Simply leaving them out of the declaration will suffice meaning it will cause them to be ignored when deciding on which language to show up on the page(s).

Localization File Formats

Each localization file is pretty simple. It consists of a flat JSON object:

    "helloWorld": "Hello World",
    "yes": "Yes",
    "no": "No"

The key is used to look up the localized string, the value will be returned from the lookup.

Parameterized Substitutions of String Text in Tokens

As mentioned earlier, this plugin is able to handle substitutions of tokens based on arguments passed to it along with the token, provided that the token contains some indication of where it is to be placed within that said token. There are a few ways of doing this:

    "helloWorld": "Hello %name"
    "helloWorld": "Hello {1}",
    "helloWorld": "Hello {firstName} {lastName}"
    "helloWorld": "Hello %1 %2"

Please take note of the fact that multiple ordered params may also be given to it.

Usage Examples

i18n directive

Localize Using the i18n attribute

The localization key can be defined as the value of the i18n attribute:

<any i18n="common.helloWorld"></any>

If the attribute value is not a valid token, then it will itself be used as the element's content.

NOTE: Localizations defined by the i18n attribute cannot contain HTML tags, as the translation result will be assigned as text, not as HTML. This limitation enables a slightly faster localization, as no sanitization is required.

Localize with Dynamic User Data

It is also possible to provide dynamic user data to the translation function.

The i18n directive observes all non-directive data-* attributes and passes them as a normalized map of key/value pairs to the translation function:

<p data-i18n="common.helloWorld" data-name="{{ }}"></p>

Whenever is updated, it's indicator in the token helloWorld is subsitituted for the new value when the translation function gets called with an object, e.g. { name: 'Bob' } as an argument and the element content is then updated accordingly.

i18nAttr directive

The i18n Attribute directive is pretty much the same as the i18n directive except that it expects a json-like object structure represented as a set of key-value pair combinations. The key corresponds to the HTML attribute to be localized, and the value is the localization resource string token which will be passed to the service itself.

If you want to pass dynamic values for the string, those should come after the value for each key; the series of additional parameters is expected to be appendeded to the token, prepended with a separator so that the directive will walk through and replace the numbered place holders with their values.

NOTE: They work the same way as the original i18n directive, but instead of updating the element content, they update their associated HTML attribute.

locale Service

The locale service is an equivalent to the i18n directive and can be used to generate localized results in situations where the directive cannot be used:

angular.module('myApp', ['ngLocalize'])
    .controller('exampleCtrl', ['$scope', 'locale',
        function ($scope, locale) {
            locale.ready('common').then(function () {
                $scope.sampleText = locale.getString('common.helloWorld', {
                    firstName: 'John',
                    lastName: 'Smith'

As you can see, The locale service expects the localization key as the first argument and an optional {Object|Array|String} with user data as the second argument.

The promise returns the object containing the localization keys & values:

angular.module('myApp', ['ngLocalize'])
    .controller('exampleCtrl', ['$scope', 'locale',
        function ($scope, locale) {
            locale.ready('common').then(function (res) {
                //res --> { "helloWorld" : "Hello World!", ... }

i18n filter

The i18n filter provides the same functionality as the service.
It can be useful in templates where the localization strings are dynamic, e.g. for error messages:

<any>{{ errorMessage | i18n }}</any>

It is also possible to pass an object or an array with localization arguments or even a single string to the i18n filter:

<p>{{ errorMessage | i18n:data }}</p>

The filter also serves a special purpose targeted at maximum compatibilty with other third party plugin modules, directives, components etc. where it is not possible to provide the parameters as a separate argument. In such a situation, the token is modified to have the substitution text params appended to it like so:

angular.module('myApp', ['ngLocalize'])
    .controller('exampleCtrl', ['$scope', '$filter', 'locale',
        function ($scope, $filter, locale) {
            locale.ready('common').then(function () {
                $scope.sampleText = $filter('i18n')('common.helloWorld::["John", "Smith"]');

Notice how we use the delimiter from ngLocalize.Config's localeConf which can be changed to suit different needs and requirements as well as you see fit in your own app. The part after the token must be in a valid JSON format as either an array, object or simple string (if it is a single param that needs to be passed in).

Sample App

I've created a sample app that uses this plugin to provide the text for the entire application. I registered 'ngLocalize' in my app's dependency list and I then use a combination of ng-bind="'home.title' | i18n", {{ 'home.title' | i18n }}, data-i18n="home.title" and data-i18n-attr="{placeholder: 'home.title'} to insert the text into the page at run time along with their variously supported use-cases.


The MIT License (MIT)

Copyright (c) 2014 Rahul Doshi

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.


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