location /abc/ {
    add_header 'Access-Control-Allow-Origin' '*';
    add_header 'Access-Control-Allow-Headers' 'X-Requested-With';
    add_header 'Access-Control-Allow-Methods' 'GET, POST, PUT, DELETE, OPTIONS' always;
    add_header 'Access-Control-Allow-Headers' 'Accept,Authorization,Cache-Control,Content-Type,DNT,If-Modified-Since,Keep-Alive,Origin,User-Agent,X-Requested-With' always;
    proxy_pass http://<ip>:<port>/;
}