Simple Rack application for JavaScript I18n

gistfile1.rb

require "json"

class JavaScriptI18n
  def self.call(env)
    locale = env["PATH_INFO"][1..-4]
    if translations.key?(locale)
      [200, {"Content-Type" => "text/javascript"}, new(translations[locale])]
    else
      [404, {}, "Not found"]
    end
  end

  def self.translations
    I18n.backend.send(:init_translations) if I18n.backend.send(:translations).empty?
    I18n.backend.send(:translations).with_indifferent_access
  end

  def initialize(translations)
    @translations = translations
  end

  def each
    yield "var I18n=I18n||{};I18n.translations="
    yield @translations.to_json
    yield ";"
  end
end

gistfile2.rb

map "/javascripts/i18n" do
  run JavaScriptI18n
end
map "/" do
  run MyShinyApp::Application
end

gistfile3.rb

javascript_include_tag "i18n/#{I18n.locale}"

gistfile4.rb

require "rack/contrib/response_cache"

map "/javascripts/i18n" do
  use(Rack::ResponseCache, "public/javascripts/i18n") { |env| env["PATH_INFO"] }
  run JavaScriptI18n
end
map "/" do
  run MyShinyApp::Application
end