How to read directory contents in Node.js

Key takeaways:

• fs.readdirSync() reads directory contents synchronously. This means it blocks other code until the operation is complete.

• The function takes a path and optional options as arguments. The path specifies the directory to read, and the options can include encoding for file names.

• fs.readdirSync() returns an array of file and subdirectory names. This array can then be used to perform further operations on the directory contents.

Syntax

The following is the general syntax of fs.readdirSync(). To access the contents of any folder, we’ll pass the path to that directory as an argument to the fs.readdirSync() function. We also pass any additional object, labeled as options in the code below. The optional object contains optional parameters like a string which specifies the encoding for the file.

This method works synchronously and returns an object containing all the folder contents. This means it won’t function parallel with other code parts. This method will prevent all other code sections from executing while reading the folder contents. Hence, it’s blocking. We can loop through the obtained files and manipulate them as we like.

• Lines 1–2: We import the fs and path modules.

• Lines 4–5: Next, we save the folder’s path in my_directory_path variable.

• Lines 6–8: Lastly, we call readdirSync function, passing it my_directory_path as an argument, and then store the object returned in display_directory; we’ll use this variable to append all file names with the folder’s path and log them to the screen.

However, this isn’t the only way to expose file system data; we can achieve the same with callbacks or promises, as shown below. However, we’ll use the asynchronous counterpart of readdirSync() called readdir(). Note that asynchronous execution is how parallelism is achieved.

Asynchronous with fs.readdir() using callbacks

The following shows the general syntax for implementing fs.readdir(). We’ll use a callback function that will take the error object and files_in_directory—the object containing all the folder content—as arguments.

• Lines 1–3: We import the fs module first. Then, we store the folder path in the variable educative_folder.

• Lines 5–16: With fs.existsSync, we verify whether the folder exists; if true, we’ll move into the if block, where fs.readdir() function is called. We pass the folder path and the callback function as arguments. If the folder has been read correctly inside the callback, all the file names within that directory will be logged to the screen. Otherwise, an error will be shown.

• Lines 18–31: If the folder does not exist at the specified path, fs.mkdir(educative_folder) creates the directory at that path and then calls the fs.readdir() function in the same way.

Asynchronous with fs.readdir() using Promises

Another way of doing all the above would have been to use promises.

• Lines 1–5: Firstly, we acquire the path and node:fs/promises modules.

• Lines 6–9: Secondly, we save the folder path as my_directory_path, passing it as an argument to the promised version of readdir(). If the promise resolves successfully, we can access the object containing all the files in the .then block and log the file names to the console.

• Lines 11–13: If the promise is rejected, we can perform error handling in the .catch block; in our case, we simply log the error to the screen.

Conclusion

In conclusion, we saw how to read folder content using the fs.readdirSync() which operates synchronously. However, if we want to adapt the same method asynchronously, we’d use its counterpart fs.readdir().