Node: Filesystem core module.

node-filesystem.js

const fs = require('fs');

let readDataCallback = (err, data) => {
  if (err) {
    console.log(`Something went wrong: ${err}`);
  } else {
    console.log(`Provided file contained: ${data}`);
  }
};
fs.readFile('./finalFile.txt', 'utf-8', readDataCallback);