Express.js Make request from client-side to server-side for a JSON file

I am trying to fetch certain data from the server.

The client-side runs a function from script.js to fetch a JSON file from the server and the server will return back with the config (JSON file) which is stored in the same folder as server.js, being called config.json. So the config can be used in a script.js.

For the server I am using express.
Any help regarding this will be extremely appreciated, thanks.