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

  • Last Updated : 29 Jun, 2020

The filehandle.writeFile() method is used to defined in the File System module of Node.js. The File System module is basically to interact 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 which will write to the file.
  • options: It is an optional parameter that affects the output in someway accordingly we provide it to the function call or not.
    • encoding: It is a string that specifies the encoding technique, default value is ‘utf8’.

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




// 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 operation done to the file that not exist earlier but created at run time.




// 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}`)
}
  
var 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}`)
    })

Directory structure before running the program:

Directory structure after running the program:

Output:




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