How to catch an error when downloading a file from a single page application?

Question

JavaScript

In a single-page application for downloading files, I redirect to a URL that gives the content of the file, content0disposition: attachment, the file offers to save, while the browser remains on the original page. Things are good.
But sometimes the file is not ready yet, and then I return the status 204 No Content instead of the file - and just nothing happens. In the body of the response I give an error message, but it does not get anywhere.
How can I get the 204 response body from the original page?
Or what is the best way to organize the case of a missing file during a redirect? It is necessary that the browser stays on the page so as not to break the application.
Option to make additional request before downloading, checking if there is a file - not ice, an extra request. At the very least, I'll stop there.

Answer 1

Look for information about XHR2, the "blob" response type, create a link on the client to the generated object from the received blob, and figure out how the user can follow (or follow) this link.