Backbone Rest Service XML output download as a xml file

We have a requirement where the service returning the XML data with the content-type: text/xml. I need to just take that content and download it in the button click through my web application HTML page. It should be shown with Open/Save option at the bottom of the web page.

We cannot use c# for this since we are using javascript to call the rest api and get the response content as xml.Is there any simple way to achieve this? Earliest help would be appreciated

Thanks,