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Node.js | fs.readdir() Method

  • Difficulty Level : Medium
  • Last Updated : 26 Mar, 2020

The fs.readdir() method is used to asynchronously read the contents of a given directory. The callback of this method returns an array of all the file names in the directory. The options argument can be used to change the format in which the files are returned from the method.

Syntax:

fs.readdir( path, options, callback )

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

  • path: It holds the path of the directory from where the contents have to be read. It can be a String, Buffer or URL.
  • options: It is an object that can be used to specify optional parameters that will affect the method. It has two optional parameters:
    • encoding: It is a string value which specifies which encoding would be used for the filenames given to the callback argument. The default value is ‘utf8’.
    • withFileTypes: It is a boolean value which specifies whether the files would be returned as fs.Dirent objects. The default value is ‘false’.
  • callback: It is the function that would be called when the method is executed.
    • err: It is an error that would be thrown if the operation fails.
    • files: It is an array of String, Buffer or fs.Dirent objects that contain the files in the directory.

Below examples illustrate the fs.readdir() method in Node.js:

Example 1: This example uses fs.readdir() method to return the file names or file objects in the directory.






// Node.js program to demonstrate the
// fs.readdir() method
  
// Import the filesystem module
const fs = require('fs');
  
// Function to get current filenames
// in directory
fs.readdir(__dirname, (err, files) => {
  if (err)
    console.log(err);
  else {
    console.log("\nCurrent directory filenames:");
    files.forEach(file => {
      console.log(file);
    })
  }
})
  
// Function to get current filenames
// in directory with "withFileTypes"
// set to "true" 
  
fs.readdir(__dirname, 
  { withFileTypes: true },
  (err, files) => {
  console.log("\nCurrent directory files:");
  if (err)
    console.log(err);
  else {
    files.forEach(file => {
      console.log(file);
    })
  }
})

Output:

Current directory filenames:
index.js
package.json
text_file_a.txt
text_file_b.txt

Current directory files:
Dirent { name: 'index.js', [Symbol(type)]: 1 }
Dirent { name: 'package.json', [Symbol(type)]: 1 }
Dirent { name: 'text_file_a.txt', [Symbol(type)]: 1 }
Dirent { name: 'text_file_b.txt', [Symbol(type)]: 1 }

Example 2: This example uses fs.readdir() method to return only the filenames with the “.txt” extension.




// Node.js program to demonstrate the
// fs.readdir() method
  
// Import the filesystem module
const fs = require('fs');
const path = require('path');
  
// Function to get current filenames
// in directory with specific extension
fs.readdir(__dirname, (err, files) => {
  if (err)
    console.log(err);
  else {
    console.log("\Filenames with the .txt extension:");
    files.forEach(file => {
      if (path.extname(file) == ".txt")
        console.log(file);
    })
  }
})

Output:

Filenames with the .txt extension:
text_file_a.txt
text_file_b.txt

Reference: https://nodejs.org/api/fs.html#fs_fs_readdir_path_options_callback




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