File system in Node.js

4 min readOct 1, 2022

Basic article on file handling in Nodejs. File System module with read, write and delete operations.

File system concept

A file system is the structure of the operating system to organize, control and store data. File systems, in addition to control, add some additional features such as access layers, attributes, and conventions.

File systems in particular act in the OS as an interface to all other devices connected to the computer (USB sticks, external drives, etc). Currently, there are different types of file systems depending on the host OS, such as Windows, macOS, or Linux. These systems have some similarities, although in principle they are incompatible with each other.

The most common file systems to date are:

Windows / FAT16, FAT32, exFAT y NTFS.
MacOs / HFS+ y APFS.
Linux / Ext4.

NOTE 🧐: To check the file system of your computer, consult the documentation of the respective OS. Windows example.

File concept

As related above, a file is basically a sequence of bytes that are stored on the device. They are called files because they are equivalent to physical files such as papers, notebooks, etc.

The particularity of the files is that they have a name and an associated extension commonly made up of 3 or 4 letters. The extension describes the content of the file, helping programs to be able to manipulate and display the content to the user as the case may be (JPG, PNG, TXT, etc).

NOTE 🧐: To get information about a certain file, check its properties. Windows example.

Module file system

Nodejs in particular contains a core module, especially for file manipulation called Filesystem. This module helps us with file support regardless of the operating system. The module works on the basis of callbacks, streams, and events like most modules in Nodejs.

Here is an example of a Nodejs program that reads the content of a text file located in the current directory.

const fs = require('fs');

fs.readFile('./hello.txt', { encoding: 'utf8'}, (err, data)=> {
  if (err) throw err;
  console.log(data);
});

This prints the following output to the console:

hello world

NOTE 🧐: The previous result, in particular, is a buffer, when we read we must indicate the encoding to interpret the content.

Basic file handling methods

The File system module contains the following basic methods for file manipulation:

File reading: readFile y readFileSync.
Writing files: writeFile y writeFileSync.
File deletion: unlink y unlinkSync.

Depending on the needs, Nodejs provides us with these methods in an asynchronous mode by default and optionally synchronous (Sync).

File reading

Here is an example of a Nodejs program that reads the content of a text file asynchronously and synchronously.

readFile

const fs = require('fs');

fs.readFile('./words.txt', { encoding: "utf-8" }, (err, data) => {
  if (err) throw err;
  console.log(data);
});

readFileSync

const fs = require('fs');

try {
  const data = fs.readFileSync('./words.txt', { encoding: "utf-8" });
  console.log(data);
} catch (err) {
  throw err;
}

These two ways print the same result to the console:

word1 word2

Writing files

Here is an example of a Nodejs program that creates a new file and writes the content asynchronously and synchronously.

writeFile

const fs = require('fs');
const text = "Hello world";

fs.writeFile('./file.txt', text, (err) => {
  if (err) throw err;
});

writeFileSync

const fs = require('fs');
const text = "Hello world";

try {
  fs.writeFileSync('./file.txt', text);
} catch (err) {
  throw err;
}

These two ways create the file named file.txt in the current directory with the content of:

Hello world

File deletion

Here is an example of a Nodejs program that deletes a file in the current directory asynchronously and synchronously.

unlink

const fs = require('fs');

fs.unlink('./file.txt', (err) => {
  if (err) throw err;
});

unlinkSync

const fs = require('fs');

try {
  fs.unlinkSync('./file.txt');
} catch (err) {
  throw err;
}

Both of these ways delete the file.txt file in the current directory.

Resources Nodejs File System

File System API: Documentation, concepts, and examples.

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