write/append to file

write.js

import fs from 'fs';

const file = file.txt;

fs.writeFile(file,'Some text to write.', (error) => {
  if(error) {
    console.error(error);
  }
  console.log('Written!');
});

fs.appendFile(file,'Some more text to append.', (error) => {
  if(error) {
    console.error(error);
  }
  console.log('Appended!');
});

fs.appendFile('log.txt', 'new data', (error) => {
  if (error) {
    // Failed: append error
  } else {
    // Success: append success
  }
});