Append text into a file nodejs

const fs = require('fs');

fs.appendFile('message.txt', 'data to append', function (err) {
  if (err) throw err;
  console.log('Saved!');
});

If message.txt doesnt exist, It will gonna create that too

Synchronously

const fs = require('fs');

fs.appendFileSync('message.txt', 'data to append');