The JS SDK of Backend Services currently does not offer a way to cancel the request. You can vote for the feature request in our Feedback portal here
. We monitor the progress of these items regularly and prioritize our development accordingly.
May I suggest as a current workaround that you use for uploading files the REST API of Backend Services with jQuery AJAX as shown in this article?
Thus you will be able to cancel or set a timeout to the request.
I hope that this helps.