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0.3.0 • Public • Published

Free-Range App Langpack Loader

This is a project to help you with two things when developing a Free-Range App:

  • Aid in loading language files, returning promises so you can delay loading the rest of your app until your translations are available
  • Providing a thin wrapper around MessageFormat for your app to use to do replacements in display strings formatted according to the ICU string formatting standard.

Language File Loader

The main function for this is loadLangPack(), which will use the provided options to fetch a JSON file of the appropriate language, with a fallback path if the requested file can't be found.

Example usage:

var fraLangPack = require( 'fra-lang-pack' );
fraLangPack.loadLangPack( {
    langTag: 'en-CA',
    languageFileRootUrl: '',
    superagentUrl: ''
} ).then( function( langPack ) {
    // Start your app
} );

Language Fallback

If, for whatever reason, a language file can't be loaded, there is a fallback to other languages before giving up. Assuming you specified a lang tag of fr-CA, it would work like this:

  • Attempt to load fr-CA.json from the directory specified by languageFileRoot
  • If that fails, attempt to load fr.json
  • If that fails, attempt to load en.json (or what was specified by defaultLangTag)
  • If that fails, reject the promise

Loader Options

Name Required Description
langTag yes The lang tag to load everything for (eg: 'fr-US'). The desired JSON file must match this. eg: fr-US.json
languageFileRootUrl yes URL to the directory containing the JSON language files
superagentUrl yes URL to fetch Superagent from. If null the NPM package will be used instead.
defaultLangTag no Fall-back language if the desired one can't be loaded (defaults to en)


This library depends on SuperAgent (tested with ^1.2.0 and ^2.0.0), but to keep the bundle size down it does not include it directly. You are required to either pass the superagentUrl option, or someone make it available to RequireJS with the name superagent.


The Formatter is a wrapper around MessageFormat, with the Language File Loader loading the locale files for you.

Example usage: (note: this requires that the locale files have already been loaded)

var fraLangPack = require( 'fra-lang-pack' );
var formatter = new fraLangPack.Formatter( 'fr' );
var formattedString = formatter.format(
    "Hello {name}, my name is {me}",
    { name: 'World', me: 'Sam' }
console.log( formattedString ); // outputs "Hello World, my name is Sam"


npm i fra-lang-pack

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