What file should i add this code to enable CORS in node js server?

    var express = require('express')
var cors = require('cors')
var app = express()

app.use(cors())

app.get('/products/:id', function (req, res, next) {
  res.json({msg: 'This is CORS-enabled for all origins!'})
})

app.listen(80, function () {
  console.log('CORS-enabled web server listening on port 80')
})

I am trying to enable CORS in my node js server. but I don't know to what file should I append the code above. Thanks in advance!

via Mukhammad Ali