i18n-x

i18n middleware for Express, inspired by i18n-node and i18n-node-2 libraries.

In opposite to libraries mentioned above this one cannot be used separately but only as Express middleware.

This library is minimalistic and easy to use alternative to libraries mentioned above with ability to dinamically change directory with localization files (e.g. if you have several independant modules and each has own templates and own locale files).

Installation

npm i i18n-x --save

Usage

Main application:

'use strict'
 
const path         = require('path');
const express      = require('express');
const cookieParser = require('cookie-parser');
 
// this library
const i18n = require('i18n-x');
 
// create Express application
const app = express();
app.use(cookieParser());
 
// enable i18n
app.use(i18n({
      // array of locales to use in application
      locales: ['en', 'ru']
}));
 
// use Pug (formerly Jade)
app.set('view engine', 'pug');
 
// handle user request
app.get('/', (req, res) => {
    // template path
    const template = path.resolve(__dirname, 'template', 'template.pug');
 
    // current locale
    const options = { locale: req.i18n.getLocale() };
    res.render(template, options);
});
 
// run Express application
app.listen(3000, () => {
    console.log('Test app listening on port 3000!');
});

${__dirname}/template/template.pug:

doctype html
html(lang= __('lang'))
    head
        title= __('title')
 
    body
        h1= __('node-i18n-x test page')
        h2 #{__('current locale:')} #{locale}
 
        h2= __('try these links:')
        ol
            li
                a(href="/") #{__('default lang')}
            li
                a(href="/?lang=en") #{__('manually set default lang')}
            li
                a(href="/?lang=ru") #{__('russian lang')}

__() function will be exported to templates through res.locals.__().
If you need to use __() in your program directly, you should use req.i18n.__().

locales/en.json:

{
    "lang": "en",
    "title": "Page title",
    "node-i18n-x test page": "Test page of node-i18n-x",
    "try these links:": "Try these links:",
    "default lang": "Default language",
    "manually set default lang": "Manually set default language",
    "russian lang": "Russian localization",
}
 

You need file with the same structure named ru.json to contain translation for key phrases from template. If there is no such file then it will be created automatically with all keys you used in templates or in program itself using __() function.

locales in current application is default directory to store localization JSON files. You can change it per application in i18n({baseDir, directory}) function or per request using req.i18n.setBaseDir() and req.i18n.setDirectory().

Path to localization JSON files defined using baseDir and directory in the following way:
baseDir + directory + '/*.json'

All localization files cached by library when they are first used so you don't need to worry about file system performance.

API

i18n(options)

This is the only function exported by i18n-x. Used to initialize Express middleware.

Parameters

options

Key-value object with the following optional keys:

{
      locales                 : ['en']
    , defaultLocale           : 'en'
    , convertLocaleToLowerCase: true
    , jointDir                : 'locales'
    , baseDir                 : '.'
    , directory               : 'locales'
    , queryParamName          : 'lang'
    , cookieName              : 'lang'
    , sessionVarName          : 'lang'
    , envVarName              : 'LANG'
    , json_space              : 4
    , order: [
          'query'
        , 'session'
        , 'cookie'
        , 'subdomain'
        , 'headers'
        , 'environment'
    ]
}

locales

array containing strings with locales your application supports.
Default: ['en']

The only parameter you really need to start wotking with the library. Provided values can be used as values of corresponding cookies, query params, subdomains, etc. You also need localization JSON files with names from this array and .json extention.

defaultLocale

string containing locale to use when other locale is not provided to your application or can't be defined for some reason.
Default: 'en'

convertLocaleToLowerCase

boolean When true then locales set from setLocale() functions will automatically be converted to lowercase. So it will always use en.json when you call setLocale('En'), setLocale('eN'), setLocale('EN') manually or some of setLocaleFrom***() called automatically.
Default: true

jointDir

string containing directory with localization files common for all application.
Default: 'locales'

This directory will be read and cached at the start of the application when library initialized and it cannot be changed later. Use it to localize common parts of application, e.g. main menu or footer.

If you use the same localization string in this common file and in unit specific file defined by baseDir and directory then value from specific file will be used.

If this directory or file for some language not exists then it will be ignored.

baseDir

string containing base directory for constructing localization file path
Default: '.'

Path to localization JSON files defined using options.baseDir and options.directory in the following way:

path = require('path');
path.join(options.baseDir, options.directory, `${locale}.json`

where locale is one of options.locales.
If directory or filename not exists then it will be created by this library.

directory

string containing directory for constructing localization file path
Default: 'locales'

See baseDir description above to know how Path to localization files defined.

queryParamName

string containing query string parameter (e.g. ?lang=ru) to define localization
Default: 'lang'

This parameter will be automatically used by library to define current locale.

cookieName

string containing name of cookie to define localization
Default: 'lang'

This parameter will be automatically used by library to define current locale. Note that you need to load special Express middleware to work with cookies before using this library.

sessionVarName

string containing name of session variable to define localization
Default: 'lang'

This parameter will be automatically used by library to define current locale. You probably need Express middleware to work with sessions to be loaded before this library.

envVarName

string containing name of environment variable to define localization
Default: 'LANG'

This parameter will be automatically used by library to define current locale.

json_space

[integer, string] contain third parameter of JSON.stringify() function which used to store localization files
Default: 4

order

array containing strings to define order of checks used to define current locale
Default:

[
      'query'       // use GET query string to define locale
    , 'session'     // use session
    , 'cookie'      // use cookie
    , 'subdomain'   // use domain with biggest level, i.e. 'ru' in ru.zerofq.com
    , 'headers'     // use Accept-Language HTTP request header
    , 'environment' // use environment variable (i.e. for electron apps)
]

You can remove any of these params (or even all of them to set locale manually with req.i18n.setLocale() function) or place them in order you wish.

Locale will be set by first acceptable method in array. That means that for default value of order locale will be set by query if it exists and correct. If query parameter from options.queryParamName does not exists in query then locale will be set from session. If there is no session or there are no options.sessionVarName in session then cookie will be used and so on. If locale could not be set by any of mentioned methods then default locale (options.defaultLocale) will be used.

Example

const i18n = require('i18n-x');
 
app.use(i18n({
      locales      : ['en', 'ru']
    , defaultLocale: 'ru'
    , baseDir      : path.join(__dirname, 'index')
    , order        : ['query', 'session']
}));

After applying middleware you can use i18n object in Express request object in all other middlewares:

app.get('/', (req, res) => {
    const options = { locale: req.i18n.getLocale() };
});

Also you can use __() function in your templates:

doctype html
html(lang= __('lang'))
    head
        title= __('title')
    body
        h1= __('node-i18n-x test page')

req.i18n

req.i18n.getLocales()

Return array of locales used by application. It is value defined in options.locales.

Return array Locales.

req.i18n.getLocale()

Return current locale automatically defined by library using methods mentioned in options.order. It always one of options.locales values.

Return string Current locale.

req.i18n.getDefaultLocale()

Return default locale. Can be used in templates, e.g. to avoid creating subdomain for default locale when using domain defined locales, so you can use ru.example.com, es.example.com and just example.com instead of en.example.com. It is options.defaultLocale value.

Return string Default locale.

req.i18n.setLocale(locale)

Allows you to set locale manually.

Param string locale Locale you want to use in current request. Should be one of options.locales.

Return boolean If locale was successfully set by this function call then return value is true. If function fails for some reason (i.e. you used string nod defined in options.locales) then it returns false and does not change locale previously defined by library.

req.i18n.setBaseDir(dirname)

Set base directory for localization files. This function affects only on current request and doesn't change options set in i18n().

It's recommended that you will change only baseDir in your code and don't touch directory option. Using this function you can organise your project this manner:

+ root app dir/
    |- app.js
    +- routes/
        +- main/
        |   |- route.js
        |   |- template.pug
        |   +- locales/
        |       |- en.json
        |       |- ru.json
        |
        +- unit1/
        |   |- route.js
        |   |- template.pug
        |   +- locales/
        |       |- en.json
        |       |- ru.json
        |
        +- unit2/
        |   |- route.js
        |   |- template.pug
        |   +- locales/
        |       |- en.json
        |       |- ru.json
        ...

In this example you should write your routes something like this:

app.get('/1', (req, res) => {
    // base directory is directory where this route allocated
    const baseDir = __dirname;
 
    const template = path.join(baseDir, 'template.pug');
 
    // now localisation files will be in `${__dirname}/locales/`
    req.i18n.setBaseDir(baseDir);
 
    res.render(template, options);
});

Param string dirname Directory path.

req.i18n.setDirectory(dirname)

Set trailing part of path where localization JSON files allocated. This function affects only on current request and doesn't change options set in i18n().

Default value is locales and you probably don't need to change it using this function, but you can change baseDir instead.

If you want to change this directory to whole application you can do it in i18n(options) while middleware initialization.

Param string dirname Directory path.

req.i18n.__(str, params = null)

Translate string using str as key in localization file defined by current locale.

Param string str String to translate.
Param array params Array of arguments to use in vsprintf() function from sprintf library or null if there is no need to additionally format string (default).

req.i18n.dumpAllStrings(locale)

Dump all strings according to provided or current locale.

Param [null, string] locale Locale to use in translation.

Return object Object containing kay-value pairs with key strings and their translations.