So, we have an existing Rails 2.3.5 app that does not support Internationalization at all. Now, I\'m well familiar with Rails I18n stuff, but we have a LOT of output strings
I18n-js is working great for me and i'd recommend it. If you use his rewrite branch then the plugin will include a /assets/i18n/filtered.js file which outputs exactly what @ryan-montgomery answered, without having to do anything yourself manually.
This way, you can use the same translations on the backend
with Rails helpers t(:key) and using I18n.t('key') in Javascript on the frontend.