Serve static app like Create React App from Nginx subdirectory

appdomain.conf

# Example config for serving a static page under nginx subdirectory
# Include this config in your server block and change the paths
#
# This is useful because we can server the same app from /subdirectory/subsubdirectory
# Where the subsubdirectory could represent :slug or :id in the client side routing.

location ^~ /subdirectory/ {
    alias /path/to/static/webroot/;

    if (!-e $request_filename) {
        rewrite ^ /subdirectory/index.html last;
    }

    location ~ \.html$ {
        if (!-f $request_filename) {
            return 404;
        }
    }

    # Replace source paths with domain prefixed ones.  
    subs_filter href="/ href="https://appdomain.domain/;
    subs_filter src="/ src="https://appdomain.domain/;
  
    # If you're using create-react-app it can also be useful to set 
    # PUBLIC_URL=https://appdomain.domain/ in .env before building
}

# Note: This is only useful for serving client side apps.
#
# To run Node on the server look into pm2 
# http://pm2.keymetrics.io/
#
# And use reverse proxy approach (proxy_pass) for the Nginx config 
# https://www.digitalocean.com/community/tutorials/how-to-set-up-a-node-js-application-for-production-on-ubuntu-16-04