I have a situation where I need to give my users the option to save some data stored locally in their client memory to disk. The current workaround I have is having a handler like this

(define-handler (download-deck) ((deck :json))

  (setf (header-out :content-type) application/json

    (header-out :content-disposition) attachment)

  deck)

which does exactly what it looks like. The client sends their data up, and saves the returned file locally.

This seems stupid.

Please, please tell me there's a better, simpler, cross-browser way to let a client save some local data to their disk with a file-save dialog box.

Every answer I read on the subject either says no, you can't save files with javascript or yes, there's this one semi-documented piece of the Chrome API that might let you do it in three pages.