update, replace_html

http://api.rubyonrails.org/classes/ActionView/Helpers/PrototypeHelper/JavaScriptGenerator/GeneratorMethods.html#M001645
replace_html可以用partial 去取代

   render :update do |page|
     page.replace_html 'target_type_target_type_id',
                       :partial => 'target_type_select', :locals => {:types => target_type_content}
   end