How to Append Data to a File using Node FS

Photo by moises ferreira on Unsplash

To append data to file in Node.js, use Node FS appendFile() function for asynchronous file operation or Node FS appendFileSync() function for synchronous file operation.

Example 1 — Node.js Append data to file asynchronously using appendFile()

var fs = require('fs');
var data = "\nAdd this line to the file.";

// append data to file
fs.appendFile('sample.txt',data, 'utf8',
// callback function
function(err) {
if (err) throw err;
// if no error
console.log("Data is appended to file successfully!")
});

Output of the file sample.txt:

Add this line to the file.

Example 2 — Node.js Append data to file synchronously using appendFileSyc()

var fs = require('fs');
var data = "\n\nAdd this line to the file.";
// append data to file
fs.appendFileSync('sample.txt',data, 'utf8');
console.log("Data is appended to file successfully.")