I am looking for a very lightweight library for uploading files asynchronously.

It is for a Rails project being updated to Rails 5.

dropzone.js was tried and sort of worked, but there was no way to tell it the upload is complete, plus the documentation sucks beyond words.

Remotipart is broken in Rails 5. It uploads fine but triggers the controller to respond to the browser which than causes a header already sent error when I try to send custom data back to the browser.

When I mean lightweight, I mean I don't care about progress bars, or any fluffery like drag and drop. Not relying on JQuery is a huge plus. Too often, JQuery plugins break when Rails updates JQuery so I avoid them like the plague.

Thanks