Lingua

Lingua is a middleware for the Express.js framework that helps you to internationalise your webapp easily. It determines the language of the user agent and pushes the i18n resources to your views.

Installation

$ npm install lingua

Quick Start

Using lingua comes down with four simple steps:

1. Grab lingua

    
   var express = require('express'),
       lingua  = require('lingua');
    
   ...
   // Express init code goes here
   ...    
    
   // Express app configuration code and lingua init.
   app.configure(function() {
       ...
       app.set('views', __dirname + '/views');
       app.set('view engine', 'ejs');
    
       // Lingua configuration
       app.use(lingua(app, {
           defaultLocale: 'en',
           path: __dirname + '/i18n'
       }));
    
       app.use(express.bodyParser());
       app.use(express.methodOverride());
       app.use(express.static(__dirname + '/public'));
       app.use(app.router);
    
       ...
   });

   Note: Please ensure that the call: "app.use(app.router);" is the last entry in your configuration section.

2. Create i18n resource files - Note that you have to create a resource file for your default language. (In this example: './i18n/en.json' and './i18n/de-de.json').

   // en.json
       {
           "title": "Hello World",
           "content": {
               "description": "A little description."
           }
       }
    
   // de-de.json
       {
           "title": "Hallo Welt",
           "content": {
               "description": "Eine kleine Beschreibung."
           }
       }

3. a. Use lingua in your views - Static output - Note that the syntax depends on your template engine. In this example it is: ejs and the request comes from a browser which sends 'en' with the HTTP request header.

   <h1><%= lingua.title %></h1> <!-- out: <h1>Hello World</h1> -->
   <p><%= lingua.content.description %></h1> <!-- out: <p>A little description.</p> -->

   b. Use lingua in your views - Dynamic output - Sometimes it is necessary to handle dynamic data within your express route and pass it to the template. What if your i18n resource includes placeholders ("{key}") within a string where you can put in your dynamic data? Well, it is possible. First of all, look at this i18n resource file:

   // de.json
   {
       "greeting": "Hallo {name}. Dieser Schlüssel {code} wurde für Dich generiert."
   }

   Now it is possible to transfer an object from your route into your template:

   app.get('/', function(req, res) {
       var names = ['Sarah', 'Thomas', 'Claudia'];
    
       res.render('index', {
           person: {
               name: names[Math.floor(Math.random()*names.length)],
               code: Math.round(Math.random()*100)
           }
       });
   });

   And finally you can execute the i18n resource (yes, you can execute it (: ) and pass your data model to this function:

   <p><%= lingua.greeting(person) %></p>

   Note: Every i18n resource which contains placeholders like in the example above is a function after you've started the application.

4. Let the user select a language - Note that the user's selection is persisted within a cookie. This is an optional step. If you want to let lingua determine the user language from the browser configuration then leave this step out. Anyway, this is a very handy feature for switching the language by a user decision.

   <a href="?language=de-DE">de-DE</a>
   <a href="?language=en-US">en-US</a>

   You can configure lingua in order to change the name of this parameter.

    
   // Express app configuration code and lingua init.
   app.configure(function() {
       ...
    
       // Lingua configuration
       app.use(lingua(app, {
           defaultLocale: 'en',
           path: __dirname + '/i18n',
           storageKey: 'lang' // http://domain.tld/?lang=de
       }));
    
       ...
   });

   The cookie lingua uses expires in one year, and includes the httpOnly flag to prevent clientside access from Javascript. You can override these settings by providing a cookieOptions key during configuration.

    
   // Express app configuration code and lingua init.
   app.configure(function() {
       ...
    
       // Lingua configuration
       app.use(lingua(app, {
           defaultLocale: 'en',
           path: __dirname + '/i18n',
           storageKey: 'lang', // http://domain.tld/?lang=de
           cookieOptions: {
               domain: '.domain.tld',    // to allow subdomains access to the same cookie, for instance
               path: '/blog',            // to restrict the language cookie to a path
               httpOnly: false,          // if you need access to this cookie from javascript on the client
               expires: new Date(Date.now() + 24 * 60 * 60 * 1000),  // expire in 1 day instead of 1 year
               secure: true              // for serving over https
           }
       }));
    
       ...
   });

Example Application

There is an example application at ./example

To run it:

$ cd example
$ node app.js

You can find a deployed version of this app here.

License

MIT License

Author

Copyright (c) 2013, André König