readwritefile.js

const fs = require("fs");

//const data = fs.readFileSync('input.txt');

//console.log(data.toString());
//console.log("Program Ended");

fs.readFile('input.txt', (err, data) => {
 if (err){
 console.log(err.stack);
 return;
 }
 console.log(data.toString());
});

console.log("Program Ended");

console.log("Going to write into existing file");
fs.writeFile('input.txt', 'Simply Easy Learning Node!', function(err) {
 if (err) {
 return console.error(err);
 }

 console.log("Data written successfully!");
 console.log("Let's read newly written data");
 fs.readFile('input.txt', function (err, data) {
 if (err) {
 return console.error(err);
 }
 console.log("Asynchronous read: " + data.toString());
 });
});