Node.js fs.readdir() method

In this article, we will discuss the Node.js fs.readdir() method with its syntax, parameters, and several examples.

What is the Node.js fs.readdir() Method?

In Node.js, the fs.readdir() method is used to read a directory's contents asynchronously. It gets an array of all the filenames in the given directory, except "." and "..". In this method, the Node.js fs module provides the file system-related operations. The format in which the files are returned by the method can be modified using the options argument.

Syntax:

It has the following syntax:

Parameters:

• fs: It is the built-in Node.js module known as "file system". In a Node.js application, this module offers methods for working with the file system.
• readdir: It is the fs module method for asynchronously reading a directory's contents.
• path: The path to the directory whose contents we wish to read is represented by this mandatory parameter. The directory path may be either in a string or a buffer.
• options: This optional parameter is an object with options for reading the directory specified in it. It is optional, and if given, it may have properties like:
  1. Encoding: The character encoding to be used when reading directory entries is specified and set to 'utf8' by default.
  2. withFileTypes: If this parameter is set to true, "fs.Dirent" objects rather than strings will be included in the callback's array of file names. By default, it sets to false.
• callback: Once the contents of the directory have been read, this callback function will be invoked. There are two parameters:
  1. err: It is an instance of Error or null if an error occurred, denoting an error object.
  2. files: It is an array of strings that represent the names of the files and subdirectories in the directory, or fs.Dirent objects if options.withFileTypes is set to true.

Example 1:

Let us take an example to illustrate the Node.js fs.readdir() method.

Output:

 The filenames in the current directory are: index.js The files in the current directory is: Dirent { name: 'index.js', [Symbol(type)]: 1 } 

Explanation:

In this example, this Node.js script makes use of the fs module to read the contents of the current directory asynchronously. If the "withFileTypes" option is set to true, both the filenames in the directory and the file information are retrieved by using the "readdir()" method twice. Every call handles any potential errors and prints its results on the console. Filenames or file objects (files) in an array and an error object (e) are sent to the callback functions. Either way, if an error occurs, it's logged to the console; if not, iteratively logging the filenames or file objects happens. The directory path of the executing script is represented by the "__dirname" variable.

Example 2:

Let us take another example to illustrate the Node.js fs.readdir() method.

Output:

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

Explanation:

In this example, this Node.js script makes use of the fs and path modules to read the contents of the current directory asynchronously. It makes use of the path.extname() function and the filter() method to filter filenames ending in ".txt". The console is logged with any errors that occur while the directory is being read. The ".txt" extension is printed to the console for all other filenames. The path to the directory where the script is currently being executed is represented by the variable "__dirname".

Conclusion:

In conclusion, the fs.readdir() method in Node.js provides asynchronous directory reading capabilities, making it an essential tool for working with the file system. With fs.readdir(), developers can create scalable and effective applications that interact with files and directories with ease, whether they are retrieving file listings, processing directories, or performing batch operations. For file system operations in Node.js applications, its asynchronous nature, flexibility, and Error handling make it a key feature.