Node.js Append to a File

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.

In this tutorial, we shall learn

Node.js Append File

Syntax – appendFile()

The syntax of appendFile() function is

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fs.appendFile(filepath, data, options, callback_function);

Callback function is mandatory and is called when appending data to file is completed.

Syntax – appendFileSync()

The syntax of appendFileSync() function is

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fs.appendFileSync(filepath, data, options);

where :

  • filepath [mandatory] is a String that specifies file path
  • data [mandatory] is what you append to the file
  • options [optional] to specify encoding/mode/flag

Note : If file specified does not exist, a new file is created with the name provided, and data is appended to the file.

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

To append data to a file asynchronously in Node.js, use appendFile() function of Node FS as shown below.

nodejs-append-to-file-example.js

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// Example Node.js program to append data to file
var fs = require('fs');

var data = "\nLearn Node.js with the help of well built Node.js Tutorial.";

// 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

arjun@arjun-VPCEH26EN:~/nodejs$ node nodejs-append-to-file-example.js
Data is appended to file successfully.

File before appending

Welcome to www.tutorialkart.com.

File after appending

Welcome to www.tutorialkart.com.
Learn Node.js with the help of well built Node.js Tutorial.

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

To append data to a file synchronously in Node.js, use appendFileSync() function of Node FS as shown below.

nodejs-append-to-file-example-2.js

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// Example Node.js program to append data to file
var fs = require('fs');

var data = "\nLearn Node.js with the help of well built Node.js Tutorial.";

// append data to file
fs.appendFileSync('sample.txt',data, 'utf8');
console.log("Data is appended to file successfully.")

Output

arjun@arjun-VPCEH26EN:~/nodejs$ node nodejs-append-to-file-example-2.js
Data is appended to file successfully.

File before appending

Welcome to www.tutorialkart.com.

File after appending

Welcome to www.tutorialkart.com.
Learn Node.js with the help of well built Node.js Tutorial.

Conclusion

In this Node.js Tutorial – Node.js Append to a File, we have learnt to append data to a file in Node.js, synchronously and asynchronously using appendFileSync() and appendFile() functions of Node FS respectively with Example Node.js programs.