Exporter is a generic export class which takes any Ext.data.Store-based component (e.g. grids and similar) and exports the data in any format.
Exporter works completely client-side. It uses a Formatter class to generate a document (.xls, .csv etc) and then uses the donwloadify library so that the user can view or download it.
Right now, there isn’t a readme or example. You can check this post for more info for now: http://www.sencha.com/forum/showthread.php?136598-Export-store-to-Excel