How to upload a file (attachment) from the browser?

I don't get attachment upload for the browser to work.

Some hints are here, others there. The docs are quite good but I'm unable to translate that to a AJAX upload.

I'm looking for a super simple HTML/JavaScript example (with or w/o jQuery) of how to upload a file from (relatively modern) browser to the db without making use of jquery.couch.app.js wrapper or stuff. The simpler the besser.

Any help appreciated.