Best way to secure single page apps?

[Klingenstein, Nate]

I read up on this a little bit for my own education.  Off the cuff, I would think the best way to do this would be by protecting a path dedicated to API's with graceful error handling in the SPA.  That kinda means moving it in the application, but maybe not horribly intrusively, especially if there can be a little flex in the "S" part of the "SPA".