Why does Angular send Http Request Method: Options before POST? - angularjs

Question

I'm using Angular Dart V1 for a front end framework
I am using shelf && shelf router for a backend API
I'm trying to migrate some old get requests to accept Post Data
Old request:
Future fetchRoutes(FlightPostParamsVO params) async {
return _http.get(BASE + 'routes').then(handleRoutes);
}
New Request
Future fetchRoutes(FlightPostParamsVO params) async {
Map post = params.toPostable();
return _http.post(BASE + 'routes', post ).then(handleRoutes);
}
I'm setting the CORS headers in a generic response for all calls as its strictly a JSON API:
Future<Response> makeResponse( json ) async {
var response = new Response.ok( json, headers: {'content-type': 'text/json',
'Access-Control-Allow-Origin': '*',
'Access-Control-Allow-Headers': "Origin, X-Requested-With, Content-Type, Accept",
'Access-Control-Allow-Methods': "POST, GET, OPTIONS"} );
return response;
}
I get a 404 an the following output:
OPTIONS http://localhost:1234/tickets/routes 404 (Not Found)
(index):1 XMLHttpRequest cannot load http://localhost:1234/tickets/routes. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:8080' is therefore not allowed access. The response had HTTP status code 404.
When i inspect the network traffic - all my GET request DO HAVE the correct headers
When i inspect the network traffic - my POST call is lead bya request with a method set as OPTIONS - this call does not have the headers included.
My POST route handler never gets called
Router
Router airRouter = router();
Router tickets = airRouter.child('/tickets');
tickets.add('/cities', ['GET'], controller.handleCitites);
tickets.add('/times', ['GET'], controller.handleTimes);
tickets.add('/routes', ['POST'], controller.handleRoutes);
tickets.add('/{id}/tickets/', ['GET'], controller.handleTickets);
io.serve(airRouter.handler, 'localhost', 1234);
Fix Symptom:
tickets.add('/routes', ['OPTIONS'], controller.handleRoutes);
Question: Why is the HTTP Request sending a Request Method:OPTIONS before each POST, and whats the proper way only call POST?

Answer 1

That is not angular. Its the browser. The first request of method OPTION is to test for CORS header to make sure the browser is allowed to post.
Solution:
http://thomaslockerambling.blogspot.com/2014/10/shelf-middleware-adding-cors-headers.html
Create a CORS Object and append to header
Intercept an Call to OPTIONS
Response with status code 200 OK