Passing a variable from the Server (Node.JS) to the Client

How is it possible to send a variable from the Server Side to the Client Side in Node.JS?

I have an app.js file and a public directory which holds an index.html template.

The app.js uses a basic server and the readFile function to open and display the HTML template.

The problem is I want to display a MongoDB query result on the client side in index.html

How is this possible, without the use of a framework such as Express, as I am trying to avoid that.

Thanks.