docs: def js(request):
      """Returns the javascript needed to run persona"""
      userid = authenticated_userid(request)
      user = markupsafe.Markup("'%s'")%userid if userid else "null"
      redirect_paramater = request.registry['persona.redirect_url_parameter']
      came_from = '%s%s' % (request.host_url,
                            request.GET.get(redirect_paramater, request.path_qs))
      data = {
          'user': user,
          'login': request.route_path(request.registry['persona.login_route']),
          'logout': request.route_path(request.registry['persona.logout_route']),
          'csrf_token': request.session.get_csrf_token(),
          'came_from': came_from,
          'request_params': markupsafe.Markup(request.registry['persona.request_params']),
      }
      template = markupsafe.Markup(pkg_resources.resource_string('pyramid_persona', 'templates/persona.js').decode())
      return template % data