Why empty request.FILE on preventDefault?

Question

Django

there is a form with a field for entering text and adding a file, the whole thing goes through ajax
when I add preventDefault in the script I get an empty MultiValueDict
when I remove preventDefault the file is present, but it redirects to the response json page
how to do it correctly so that you can send the file and the server does not display json view response, but left it on the same page?
code https://gitlab.com/axce1/talk