The package i18n provides the framework to support translations in your programs. This is just a basic sample to show how it could be used in a command line program - using it in a web server (express) scenario would be somewhat different as it appears to pick up the locale from the browser request. Read more on the official documentation.
Basically, you register the folder where translations are placed, and a JSON file is added for each of the registered locales that your application support. Here I have specified I support: en, en-AU, and fr. So I end up with a respective JSON file in the locales folder.
This basic example is set up just to output the greeting for each translation.
To try this program out:
git clone https://github.com/tschf/node-translation-demo
cd node-translation-demo
npm i
node index.js
Which should produce the following output:
Greeting in en is Hello
Greeting in en-AU is G'day
Greeting in fr is Bonjour
Trent Schafer
The Unlicense