Node.js fsPromises.appendFile() Function Last Updated : 08 Oct, 2021 Comments Improve Suggest changes Like Article Like Report The fsPromises.appendFile() method is used to asynchronously append the given data to a file. A new file is created if it does not exist. The options parameter can be used to modify the behavior of the operation. Syntax: fsPromises.appendFile( path, data, options ) Parameters: This method accepts three parameters as mentioned above and described below: path: It is a String, Buffer, URL or number that denotes the source filename or file descriptor that will be appended to.data: It is a String or Buffer that denotes the data that has to be appended.options: It is an string or an object that can be used to specify optional parameters that will affect the output. It has three optional parameters:encoding: It is a string that specifies the encoding of the file. The default value is ‘utf8’.mode: It is an integer which specifies the file mode. The default value is ‘0fso666’.flag: It is a string which specifies the flag used while appending to the file. The default value is ‘a’. Return Value: It returns the Promise. Example: This example uses a sample txt file named "example_file" with Hello text. Filename: index.js javascript // Node.js program to demonstrate the // fsPromises.appendFile() method // Import the filesystem module const fs = require('fs'); const fsPromises = fs.promises; // Get the file contents before the append operation console.log("\nFile Contents of file before append:", fs.readFileSync("example_file.txt", "utf8")); fsPromises.appendFile("example_file.txt", "GeeksforGeeks") .then(function(){ console.log("\nFile Contents of file after append:", fs.readFileSync("example_file.txt", "utf8")) }) .catch( function (err) { console.log(err); }); Note: Run index.js file with below command: node index.js Output: File Contents of file before append: Hello File Contents of file after append: HelloGeeksforGeeks Note: If options is a string, then it specifies the encoding. The path may be specified as a FileHandle that has been opened for appending (using fsPromises.open()). Comment More infoAdvertise with us N nitin_sharma Follow Improve Article Tags : Web Technologies Node.js Node.js-fs-module Similar Reads Node JS fs.readFile() Method ​In Node.js, the fs.readFile() method is a fundamental tool for reading files asynchronously, allowing your application to remain responsive while accessing file data. This method is part of Node.js's File System (fs) module, which provides an API for interacting with the file system.Syntaxfs.readFi 3 min read Node.js fs.exists() Method The fs exists method in node is used to check if the input file or the directory exists or not. It is an inbuilt application programming interface of fs module which provides an API for interacting with the file system in a manner closely modeled around POSIX functions. Syntax:fs.exists( path, callb 2 min read Node fs.existsSync() Method In Node.js, the fs.existsSync() method checks if a file or folder exists at a given path. It's synchronous, meaning it pauses the program until it finds the result (either true if it exists, or false if it doesn't). Because it stops everything while it works, it’s best used for quick checks in small 3 min read Node fs.mkdir() Method The fs.mkdir() method in Node.js is used to create a directory asynchronously.Syntaxfs.mkdir(path, mode, callback)Parameters: This method accepts three parameters as mentioned above and described below: path: This parameter holds the path of the directory that has to be created.mode: This parameter 2 min read Node.js fs.truncate() Method The fs.truncate() method in node.js is used to change the size of the file i.e either increase or decrease the file size. This method changes the length of the file at the path by len bytes. If len represents a length shorter than the file's current length, the file is truncated to that length. If i 2 min read Node.js fs.renameSync() Method In Node.js, the fs.renameSync() method is part of the built-in File System (fs) module and is used to rename or move files and directories synchronously. This method is useful when you need to quickly change a file's name or move it to a different directory synchronously. It blocks the execution of 3 min read Node.js fs.rmdir() Method The fs.rmdir() method is used to delete a directory at the given path. It can also be used recursively to remove nested directories.Syntax: fs.rmdir( path, options, callback )Parameters: This method accepts three parameters as mentioned above and described below: path: It holds the path of the direc 3 min read Node.js fs.stat() Method The fs.stat() method is used to return information about the given file or directory. It returns an fs.Stat object which has several properties and methods to get details about the file or directory. Syntax:fs.stat( path, options, callback )Parameters: This method accept three parameters as mentione 3 min read Node.js fs.mkdtempSync() Method The fs.mkdtempSync() method is an inbuilt application programming interface of fs module which provides an API for interacting with the file system in a manner closely modeled around standard POSIX functions. The fs.mkdtempSync() method creates a unique temporary directory. This is the synchronous v 2 min read Node.js fs.realpath() Method The fs.realPath() method is used to compute the canonical pathname of the given path. It does so by resolving the ., .. and the symbolic links in the path. Syntax: fs.realpath( path, options, callback ) Parameters: This method accept three parameters as mentioned above and described below: path: It 3 min read Like