nginx.conf for CORS

nginx_for_cors.conf

location / {
    if ($http_origin = 'http://api.example.com') {
        set $cors 'true';
    }
    if ($request_method = 'OPTIONS') {
        set $cors "${cors}:options";
    }
    if ($request_method ~ ^(POST|GET)$) {
        set $cors "${cors}:allow_methods";
    }

    if ($cors = 'true:allow_methods') {
        add_header 'Access-Control-Allow-Origin' "$http_origin";
        add_header 'Access-Control-Allow-Credentials' 'true';
        add_header 'Access-Control-Allow-Headers' 'Content-Type';
    }

    if ($cors = 'true:options') {
        add_header 'Access-Control-Allow-Origin' "$http_origin";
        add_header 'Access-Control-Allow-Credentials' 'true';
        add_header 'Access-Control-Allow-Headers' 'Content-Type';
        add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
        add_header 'Access-Control-Max-Age' 86400;
        return 204;
    }
}