Crossing the CORS

Cross Origin Resource Sharing by which you let others to access the api's hosted on your domain. 

Below (nginx) example adds the headers to default.conf file

add_header 'Access-Control-Allow-Origin' '*';

add_header 'Access-Control-Allow-Headers' 'X-Requested-With, accept, content-type';

Below are few links that I used for my reference.

How CORS works?

How to add CORS support to expressjs running node

How to add CORS support to nginx

Any client side Javascript can make calls to other website which has the above rule set. Be careful while setting  Access-Control-Allow-Origin to '*', as this allows anyone to hit your api/website