Active page checker for navigation elements within middleman app

config.rb

helpers do
  def nav_active(url)
    if (url.instance_of? String)
      current_resource.url == url_for(url) ?  {class: "active"} : {}
    elsif (url.instance_of? Array)
      url.map { |url| url_for(url) }.include?(current_resource.url) ? {class: "active"} : {}
    else
      {}
    end
  end
end