Answer 1

What happens when you execute this?

Answer 2

Alright.
If it solves your problem, mark my answer as best...

Answer 3

Ohk, so have you defined it first?
It should be something like

var fs = require('fs');

OR

const fs = require('fs');

This should be at the beginning.
fs is the file system module of Node.js, but you have to include it first to use it...

Answer 4

So is it solved?