Is multithreading used in Node.js when interacting with the file system?

Yes, in Node.js, multithreading is used when interacting with the file system, even though JavaScript itself in Node.js is single-threaded.

Node.js uses an internal thread pool (libuv thread pool) to perform input/output operations, including working with the file system. This allows the main thread to remain unblocked and handle other events while file operations are performed in the background.

Example of asynchronous file reading:

const fs = require('fs');

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

In this example, the file reading occurs in a separate thread from the pool, while the main thread continues to work.