jQuery File Upload is a pretty capable file uploader with some nice features, but I've found its documentation to be lacking.
There are really two components to jQuery File Upload: the front-end scripts and stylesheets, and the back-end endpoints to support it.
What you're asking about specifically are the back-end endpoints, and I think there are better packages to use. You're using blueimp-file-upload-node
, which contains a LOT of stuff you don't need for a Node implementation, such as PHP and Python implementations, as well as front-end examples.
I recommend you look at jquery-file-upload-middleware
instead. It provides Express/Connect middleware, and has better documentation. You'll still need to set up the front-end scripts per jQuery-File-Upload documetnation, but this will handle all the back-end for you.