instance method build_callbacks

# File actionpack/lib/action_view/helpers/prototype_helper.rb, line 1091
      def build_callbacks(options)
        callbacks = {}
        options.each do |callback, code|
          if CALLBACKS.include?(callback)
            name = 'on' + callback.to_s.capitalize
            callbacks[name] = "function(request){#{code}}"
          end
        end
        callbacks
      end