app/views/layouts/_javascript.html.erb
<%= javascript_include_tag 'application.js' %>
<% language = FastGettext.locale %>
<% %w{messages methods}.each do |type| %>
<% require_path = File.join('jquery-validation', 'localization', type+'_'+language) %>
<% full_path = Rails.root.join('public', 'javascripts', require_path+'.js')%>
<%= javascript_include_tag require_path if File.exists?(full_path) %>
<% end %>