Uploading file using rails.js

By default, browsers do not allow files to be uploaded via AJAX. As a result, if there are any non-blank file fields in the remote form, this adapter aborts the AJAX submission and allows the form to submit through standard means.

The ajax:aborted:file event allows you to bind your own handler to process the form submission however you wish.

     $('form').bind('ajax:aborted:file', function(event, elements){
      // Implement own remote file-transfer handler here for non-blank file inputs passed in `elements`.
      // Returning false in this handler tells rails.js to disallow standard form submission
       return false;
     });

The ajax:aborted:file event is fired when a file-type input is detected with a non-blank value.

Third-party tools can use this hook to detect when an AJAX file upload is attempted, and then use techniques like the iframe method to upload the file instead.