Introduction to the fs Module in Node.js

You’ll need to have Node.js installed first, of course. You can do that here. Luckily for us, fs is one of the ‘out-of-the-box’ modules that come with Node so it is already available to you.

const fs = require('fs');

Every fs method has both a synchronous and an asynchronous version with the name for the synchronous form just ending with Sync. So an asynchronous fs.writeFile() becomes fs.writeFileSync(). Of course, Synchronous code will stop later code from running when there is an error, but they’re simpler to get the hang of so for all of the examples in this article we’ll be using their synchronous forms.

The basic CRUD operations (create, read, update, and delete) are very simple to do with only 3 main functions.

• fs.writeFileSync()
• fs.readFileSync()
• fs.unlinkSync()

const gators = [{
  type: 'cayman'
}];

fs.writeFileSync('./swamp/cayman.json', JSON.stringify(gators));

[{"type":"cayman"}]

const gators = [{
    type: 'cayman'
}];


const getData = () => {
  let data = fs.readFileSync('./swamp/cayman.json', 'utf8');

  if (!data) return [];
  else {
    const file = JSON.parse(data);
    return file;
  }
}

const data = getData();

fs.unlinkSync('./swamp/cayman.json');

The above three methods have their own useful counterparts for manipulating directories themselves.

• fs.mkdirSync()
• fs.rmdirSync()
• fs.readdirSync()

Since the usage of fs.mkdirSync() and fs.readdirSync() are the same as their file counterparts we’ll finish up with working out the gotchas that come with fs.rmdirSync() instead.

The main problem with using fs.rmdirSync() to delete folders is the fact that it will only work on empty directories. If you were to try using it to remove ./swamp it will return:

Error: ENOTEMPTY: directory not empty, rmdir './swamp'

which obviously isn’t what we want. Sadly, Node does not have a native solution for this, for some reason, so we’ll have to look elsewhere.

The simplest solution I’ve found has been an npm package called rimraf, so let’s install that quickly.

$ npm i rimraf

The syntax is very similar, except instead of fs you call rimraf.sync() ( or plain rimraf() for the asynchronous version) and pass in your path as you would expect.

const rimraf = require('rimraf');

rimraf.sync('./swamp');

With just these few functions you’ll be able to handle many of the common use cases with manipulating files and their data.

Any introduction to a new technology will come with obligatory referral to the documentation (it really is one of the best ways to explore something).