Is it possible to override the contentType="application/json" to contentType="multipart/form-data" in backbone.js?
Any example for backbone file upload?
No, you can't do file uploads outside of an html form. What folks usually do is have a hidden iframe which hosts a form to do the upload and then have their main html page communicate with that iframe so the form post doesn't disturb your otherwise seamless SPA UX. This isn't a backbone-specific issue.