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JavaScript | Program to write data in a text File
  • Last Updated : 19 Feb, 2019

Pre-requisite: How to import a library in JavaScript. Read from here: https://www.geeksforgeeks.org/javascript-importing-and-exporting-modules/ .

There is a built-in Module or in-built library in NodeJs which handles all the writing operations called fs (File-System). It is basically a JavaScript program (fs.js) where function for writing operations is written. Import fs-module in the program and use functions to write text to files in the system. The following function will create a new file with a given name if there isn’t one, else it will rewrite the file erasing all the previous data in it.

Used Function: The writeFile() functions is used for writing operation.

Syntax:

writeFile( Path, Data, Callback)

Parameters: This method accepts three parameters as mentioned above and described below:



  • Path: It takes in relative path from the program to the text File. If the file is to be created in the same folder as that of the program, then give the name of the file only. If file not exists then new file will be created automatically.
  • Data: This argument takes in data which need to write in the file.
  • Callback Function: It is the callback function which further has an argument (err). If the operation fails to write the data, err shows the fault.

Example:




<script>
// Requiring fs module in which
// writeFile function is defined.
const fs = require('fs')
  
// Data which will write in a file.
let data = "Learning how to write in a file."
  
// Write data in 'Output.txt' .
fs.writeFile('Output.txt', data, (err) => {
      
    // In case of a error throw err.
    if (err) throw err;
})
</script>

Output:

Learning how to write in a file.

Note: Above script can be run using NodeJs interpreter in terminal.

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