Rendering templates at the root 

When the server receives a request at the root URL /, we will render template.js in the browser. In server.js, add the following route handling code to the Express app to receive GET requests at /.

mern-simplesetup/server/server.js:

import template from './../template'
app.get('/', (req, res) => {
     res.status(200).send(template())
})

Finally, add server code to listen on the specified port for incoming requests.

mern-simplesetup/server/server.js:

let port = process.env.PORT || 3000
app.listen(port, function onStart(err) {
  if (err) {
    console.log(err) 
  }
  console.info('Server started on port %s.', port)
})