local_storage.rb

module LocalStorage
  def self.[](name)
    `localStorage.getItem(name)`
  end
  
  def self.[]=(name, value)
    `localStorage.setItem(name, value)`
  end
  
  def self.key?(name)
    `localStorage.getItem(name) !== undefined`
  end
end

LocalStorage[:user_id] = User.current.id