Acheiving CORS via a Node HTTP Server

cors.js

// Create our server
var server;
server = http.createServer(function(req,res){
	// Set CORS headers
	res.setHeader('Access-Control-Allow-Origin', '*');
	res.setHeader('Access-Control-Request-Method', '*');
	res.setHeader('Access-Control-Allow-Methods', 'OPTIONS, GET');
	res.setHeader('Access-Control-Allow-Headers', '*');
	if ( req.method === 'OPTIONS' ) {
		res.writeHead(200);
		res.end();
		return;
	}

	// ...
});

The most important aspect of what differentiates this code from most stackoverflow answers / blogposts is that it returns these headers both on the prefetch response to the OPTIONS request, and on the actual response delivering the requested data.

Failing that:

If you using Chrome and your not sure what headers are being requested, use the Developer Console, Network select the call being made and you can view what headers are being requested by Access-Control-Request-Headers

(http://stackoverflow.com/questions/32500073/request-header-field-access-control-allow-headers-is-not-allowed-by-itself-in-pr)

e.g.: res.setHeader('Access-Control-Allow-Headers', 'authorization, content-type');

This did it, finally. Thanks +1(000)!