The fs.mkdirSync() method is an inbuilt application programming interface of fs module which provides an API for interacting with the file system in a manner closely modeled around standard POSIX functions.

fs.mkdirSync() Method

The fs.mkdirSync() method is used to create a directory Synchronously. If the directory already exists, an error is thrown unless the recursive option is set to true, which allows the creation of nested directories.

Syntax:

fs.mkdirSync( path, options )

Parameters:

This method accept two parameters as mentioned above and described below:

• path: The path at which directory is to be created. It can be string, buffer, etc.
• options: It is an optional parameter which determines how to create directory like recursively, etc.

Return value: It returns undefined. Below examples illustrate the use of fs.mkdirSync() method in Node.js

Example 1: This example demonstrates how to check for the existence of a directory and create it if it doesn't exist using Node.js fs.exists() and fs.mkdirSync() methods.

// Node.js program to demonstrate the
// fs.mkdirSync() method

const fs = require("fs");

const path = require("path");

// Using fs.exists() method to
// check that the directory exists or not
console.log("Checking for directory "
			+ path.join(__dirname, "Geeks"));

fs.exists(
		path.join(__dirname, "Geeks"),
			(exists) => {
				console.log(
                	exists ? 	
                    "The directory already exists" 
                    : "Not found!"
				);
});

// Using fs.mkdirSync() method
// to create the directory
fs.mkdirSync(path.join(__dirname, "Geeks"));

// Using fs.exists() method to
// check that the directory exists or not
fs.exists(
	path.join(__dirname, "Geeks"),
    (exists) => {
	console.log(
    	exists ?
        "The directory already exists" 
        : "Not found!"
	);
});

Output:

Checking for directory c:\Users\Suraj\node\Geeks
Not found!
The directory already exists

Example 2: This example checks for a directory's existence, creates it recursively if it doesn't exist, and verifies its creation using Node.js fs.exists() and fs.mkdirSync() methods

// Node.js program to demonstrate the
// fs.mkdirSync() method

const fs = require("fs");

const path = require("path");

// Using fs.exists() method to
// check that the directory exists or not
console.log(
	"Checking for directory" 
    + path.join(__dirname, "Tisu")
);

fs.exists(path.join(__dirname, "Tisu"), 
	exists => {
  		console.log(
        	exists ?
            "The directory already exists"
			: "Not found!"
		);
});

// Using fs.mkdirSync() method
// to create the directory recursively
fs.mkdirSync(path.join(__dirname, "Tisu"), true);

// Using fs.exists() method to
// check that the directory exists or not
fs.exists(
	path.join(__dirname, "Tisu"),
	exists => {
		console.log(
        	exists ?
			"The directory already exists" 
			: "Not found!"
		);
});

The above program will compile and run by using the below command.

node index.js

Output:

Checking for directory c:\Users\Suraj\node\Tisu
Not found!
The directory already exists

Summary

The fs.mkdirSync() method is a straightforward way to create directories synchronously in Node.js, especially useful when you need to ensure the existence of directories before proceeding with file operations.