1.2.3 • Public • Published

    Express it

    Serve custom translation variants for your Express 4.x app.

    $ npm install express-it --save

    Peer dependencies required

    • express: For translation center & middleware integration.
    • redis: For storing persistent translations in memory.


    If you’ve ever wanted to serve different message copy to a user based on varying cirumstances, this is the right tool.

    This tool can also be used as a light-weight solution to i18n (internationalization), however be mindful that the scope of this project is not aimed at creating custom routing, dealing with pluralisation, or custom number formatting. It can, however, live along side your existing i18n framework (if this is your desire).

    How it works

    The idea is to put the user into a custom translation variant based on any arbitrary data you see fitting. For example, several websites will use different messaging based on the users demographic, or if they were invited through a specific campaign or community.

    Thus, instead of having to do this everywhere throughout your code...

    if (user.age > 18 && user.age < 24 && user.gender == 'female') {
      render('<p>Like, hello {name}. Your totes welcome to the fridge</p>')
    else if (user.age >= 21 && user.gender == 'male') {
      render('<p>Yo {name}. The beer is in the fridge.</p>')
    } else {
      render('<p>Welcome {name}. Here is the fridge.</p>')

    You could do something like this (we’ll show you how to setup a user in a variant later):

      p!= t('welcome.fridge.msg', { name: user.first_name }).backup('Welcome {name}. Here is the fridge.')

    A fully managed translation center

    This tool comes with an administration interface (integration required) allowing you to update message copy in real-time.


    var client = require('redis').createClient()
    var VARIANTS = ['en.default', '', 'en.millenials', 'en.fb_mom_campaign', 'en.pinterest_users']
    YOUR_APP.use('/path/to/translation-center', require('express-it').init({
     express: YOUR_EXPRESS,
     redis: client,
     variants: VARIANTS
    YOUR_APP.use(function (req, res, next) {
     // this introspection can be async
     req.variant = 'en.default' // or some other variant based on user data
     redis: client,
     variants: VARIANTS


    Both client and server templates can take advantage of the t() function. The usage of the backup() method is required in all circumstances in cases where redis fails, or if a key is not found.

      p= t('welcome.msg', { name: user.first_name }).backup('Hello {name}. Welcome to our website')

    Usage from pure client-side

    // use the "E" view local to load your translations and "t()" function
        title example
        != E.getLoader()
        // etc...
    // call `t` from anywhere...
      window.t('welcome.msg', { name: user.username }).backup('Welcome to')

    Cascading variations

    One great feature ExpressIt provides is the ability to cascade a user with multiple variations. For example one user might be part of both a Pinterest Campaign variant, and millenial (age group) variant. You can set your req.variant as such in your integrated middleware.

    YOUR_APP.use(function (req, res, next) {
      req.variant = ['en.pinterest_campaign', 'en.millenial', 'en.default']

    In the example above, you may have a translation key for welcome.msg in the en.pinterest_campaign variant.

    However in the absense of a translation for the tutorial.step.1 translation key for en.pinterest_campaign, it will cascade to the next variant — which in this case is en.millenial.

    The advantage of this is that not every variant requires a translation for each key, allowing you to fallback onto other (perhaps more appropriate) messaging.


    see tests/index.js

    $ npm test


    Yes please, and always welcome! Please consider the primary goals too. This is not intended to be a full i18n replacement. However performance improvements, bug fixes, and minor feature additions are fully welcomed!

    Licence MIT

    express-it is © 2015 Dustin Diaz and licensed under MIT. All rights not explicitly granted in the MIT license are reserved. See the included LICENSE file for details.


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