I have done some research on the internet, but I didn\'t manage to get the complete picture about this subject. Can anyone help to solve this answer for now and forever?
With JSONP, setting custom headers is not possible.
With CORS, the server must send the Access-Control-Allow-Headers header to allow uncommon request headers from the client. From the HTML5 Rocks CORS page:
Access-Control-Allow-Headers... - Comma-delimited list of the supported request headers.
Thus, your server must send a Access-Control-Allow-Headers: Authorization to let the browser know it is permissible to send Authorization to the server with the request. Without this sever header, the browser will only send a few common headers with the request and ignore the rest.