Underscore-based, drop-in i18n-js replacement for Rails

app_assets_i18n.js.erb

//= depend_on_locale

I18n = {
  translations: <%= I18n.backend.send(:translations)[I18n.locale].to_json %>
};

I18n.t = (function(source) {
  var interpolationRegex = /%{([^}]+)}/g;

  return function(path, data) {
    if (_.isUndefined(data)) data = {};

    var keys = path.split('.'),
        translation = _.reduce(keys, function(currentLevel, key) {
          if (!_.isUndefined(currentLevel)) return currentLevel[key];
        }, source);

    if (!translation) return '[Missing translation: ' + path + ']';

    // Handle count properly
    if (!_.isUndefined(data.count) && _.isObject(translation)) {
      if (data.count === 0) translation = translation.zero || translation.other;
      else if (data.count === 1) translation = translation.one || translation.other;
      else translation = translation.other;
    }

    // Perform basic interpolation
    if (_.isString(translation)) {
      translation = translation.replace(interpolationRegex, function(match, name) {
        return data[name];
      });
    }

    return translation;
  };
})(I18n.translations);

config_initializers_sprockets.rb

class Sprockets::DirectiveProcessor
  def process_depend_on_locale_directive
    filename = "#{I18n.locale}.yml"

    # Ensure that I18n is loaded
    I18n.backend.send(:init_translations) unless I18n.backend.initialized?

    path = File.expand_path(filename, Rails.root.join('config', 'locales'))
    context.depend_on(path)
  end
end