How to redirect from within a .js script

I need to redirect from within an action called by an Ajax request

  def create
respond_with resource do |format|
format.js {
.. # test on user locale and changed
        I18n.default_locale =
         I18n.locale = I18n.default_locale
        session[:return_to]["locale"] = I18n.locale.to_s
@url = session[:return_to] || root_path
        session[:return_to] = nil
render :action => "signed_in.js"

I think you’d need to generate the root_path for the specific locale…

root_path(:locale =>