i18next-express-middleware/README.md

# Introduction

This is a middleware to use i18next in express.js.

# Getting started

Source can be loaded via [npm](https://www.npmjs.com/package/i18next-express-middleware).

```
# npm package
$ npm install i18next-express-middleware
```

## wire up i18next to request object

```js
var i18next = require('i18next');
var middleware = require('i18next-express-middleware');
var express = require('express');

i18next
  .use(middleware.LanguageDetector)
  .init({ 
    preload: ['en', 'de', 'it'], 
    ...otherOptions 
   });

var app = express();
app.use(middleware.handle(i18next, {
  ignoreRoutes: ["/foo"],
  removeLngFromUrl: false
}));


// in your request handler
app.get('myRoute', function(req, res) {
  var lng = req.language; // 'de-CH'
  var lngs = req.languages; // ['de-CH', 'de', 'en']
  req.i18n.changeLanguage('en'); // will not load that!!! assert it was preloaded

  var exists = req.i18n.exists('myKey');
  var translation = req.t('myKey');
});

// in your views, eg. in pug (ex. jade)
div=t('myKey')
```

## add routes

```js
// missing keys
app.post('/locales/add/:lng/:ns', middleware.missingKeyHandler(i18next));

// multiload backend route
app.get('/locales/resources.json', middleware.getResourcesHandler(i18next));
```

## add localized routes

You can add your routes directly to the express app

```js
var express = require('express'),
    app = express(),
    i18next = require('i18next'),
    FilesystemBackend = require('i18next-node-fs-backend'),
    i18nextMiddleware = require('i18next-express-middleware'),
    port = 3000;

i18next
  .use(i18nextMiddleware.LanguageDetector)
  .use(FilesystemBackend)
  .init({ preload: ['en', 'de', 'it'], ...otherOptions }, function() {
    i18nextMiddleware.addRoute(i18next, '/:lng/key-to-translate', ['en', 'de', 'it'], app, 'get', function(req, res) {
      //endpoint function
    });
  });
app.use(i18nextMiddleware.handle(i18next));
app.listen(port, function() { console.log('Server listening on port', port) } );
```

or to an express router

```js
var express = require('express'),
    app = express(),
    i18next = require('i18next'),
    FilesystemBackend = require('i18next-node-fs-backend'),
    i18nextMiddleware = require('i18next-express-middleware'),
    router = require('express').Router(),
    port = 3000;

i18next
  .use(i18nextMiddleware.LanguageDetector)
  .use(FilesystemBackend)
  .init({ preload: ['en', 'de', 'it'], ...otherOptions }, function() {
    i18nextMiddleware.addRoute(i18next, '/:lng/key-to-translate', ['en', 'de', 'it'], router, 'get', function(req, res) {
      //endpoint function
    });
    app.use('/', router);
  });
app.use(i18nextMiddleware.handle(i18next));
app.listen(port, function() { console.log('Server listening on port', port) } );
```

## language detection

Detects user language from current request. Comes with support for:

- path
- cookie
- header
- querystring
- session

Wiring up:

```js
var i18next = require('i18next');
var middleware = require('i18next-express-middleware');

i18next
  .use(middleware.LanguageDetector)
  .init(i18nextOptions);
```

As with all modules you can either pass the constructor function (class) to the i18next.use or a concrete instance.

## Detector Options

```js
{
  // order and from where user language should be detected
  order: [/*'path', 'session', */ 'querystring', 'cookie', 'header'],

  // keys or params to lookup language from
  lookupQuerystring: 'lng',
  lookupCookie: 'i18next',
  lookupSession: 'lng',
  lookupPath: 'lng',
  lookupFromPathIndex: 0,

  // cache user language
  caches: false, // ['cookie']

  // optional expire and domain for set cookie
  cookieExpirationDate: new Date(),
  cookieDomain: 'myDomain'
}
```

Options can be passed in:

**preferred** - by setting options.detection in i18next.init:

```js
var i18next = require('i18next');
var middleware = require('i18next-express-middleware');

i18next
  .use(middleware.LanguageDetector)
  .init({
    detection: options
  });
```

on construction:

```js
var middleware = require('i18next-express-middleware');
var lngDetector = new middleware.LanguageDetector(null, options);
```

via calling init:

```js
var middleware = require('i18next-express-middleware');

var lngDetector = new middleware.LanguageDetector();
lngDetector.init(options);
```

## Adding own detection functionality

### interface

```js
module.exports {
  name: 'myDetectorsName',

  lookup: function(req, res, options) {
    // options -> are passed in options
    return 'en';
  },

  cacheUserLanguage: function(req, res, lng, options) {
    // options -> are passed in options
    // lng -> current language, will be called after init and on changeLanguage

    // store it
  }
};
```


### adding it

```js
var i18next = require('i18next');
var middleware = require('i18next-express-middleware');

var lngDetector = new middleware.LanguageDetector();
lngDetector.addDetector(myDetector);

i18next
  .use(lngDetector)
  .init({
    detection: options
  });
```