Node.js filehandle.writeFile() Method from class: FileHandle

Last Updated : 06 Apr, 2023

The filehandle.writeFile() method is used to define in the File System module of Node.js. The File System module basically interacts with the hard disk of the user’s computer. The fs.writeFile() method asynchronously writes data to a file, replacing the file if it already exists.

Syntax:

filehandle.writeFile(data, options)

Parameter: This method accepts two parameters as mentioned above and described below:

data: It is a String, Buffer, or Uint8Array instance. It is the data that will write to the file.
options: It is an optional parameter that affects the output in some way accordingly we provide it to the function call or not.
- encoding: It is a string that specifies the encoding technique, the default value is ‘utf8’.

Example 1: This example explains how to write operations done to the file that already exists.

javascript

// Node.js program to demonstrate the
// filehandle.writeFile() Method

// Importing File System and Utilities module
const fs = require('fs')

// The readFileSync() method reads the
// contents of the file and returns the
// buffer form of the data
const oldBuff = fs.readFileSync('./tesTfile.txt')
const oldContent = oldBuff.toString()
console.log(`\nOld content of the file :\n${oldContent}`)

const writeToFile = async (path, data) => {
    let filehandle = null

    try {
        filehandle = await fs.promises.open(path, mode = 'w')
        // Write to file
        await filehandle.writeFile(data)
    } finally {
        if (filehandle) {
            // Close the file if it is opened.
            await filehandle.close();
        }
    }
    // New content after write operation
    const newBuff = fs.readFileSync('./tesTfile.txt')
    const newContent = newBuff.toString()
    console.log(`\nNew content of the file :\n${newContent}`)
}

writeToFile('./testFile.txt', "Hey, I am newly added!")
    .catch(err => {
        console.log(`Error Occurs, Error code ->
            ${err.code}, Error NO -> ${err.errno}`)
    })

Output:

Example 2: This example explains how to write operations done to the file that did not exist earlier but was created at run time.

javascript

// Node.js program to demonstrate the
// filehandle.writeFile() Method

// Importing File System and Utilities module
const fs = require('fs')

const writeToFile = async (path, data) => {
    let filehandle = null

    try {
        filehandle = await fs
            .promises.open(path, mode = 'w')
        // Write to file
        await filehandle.writeFile(data)
    } finally {
        if (filehandle) {
            // Close the file if it is opened.
            await filehandle.close();
        }
    }
    // The readFileSync() method reads
    // the contents of the file and
    // returns the buffer form of the data
    const buff = fs.readFileSync(path)
    const content = buff.toString()
    console.log(`\nContents of the file :\n${content}`)
}

let query = "Hey there, I am newly added "
    + "content of newly added file!";
writeToFile('./testFile.txt', query)
    .catch(err => {
        console.log(`Error Occurs, Error code ->
        ${err.code}, Error NO -> ${err.errno}`)
    })