Promisified node.js file system utilities

Originally published on davidwells.io

Node introduced the promisify utilities in back in version 8.

Using promisify you can use the node.js file system utilities with async/await and promises.

There are a couple of bits missing from the core node.js filesystem.

Below are the promisified file system calls I use a bunch in projects.

I've added createDir, fileExists, and deleteDir to smooth over some of the core fs methods that can be a little awkward to work with.

/* ./utils/fs.js */
const fs = require('fs')
const mkdirp = require('mkdirp')
const rimraf = require('rimraf')
const { promisify } = require('util')

const fileExists = (s) => new Promise(r => fs.access(s, fs.F_OK, e => r(!e)))

module.exports = {
  // Check if file exists
  fileExists: fileExists,
  // Read file
  readFile: promisify(fs.readFile),
  // Write file
  writeFile: promisify(fs.writeFile),
  // Recursively create directory
  createDir: mkdirp,
  // Read directory file names
  readDir: promisify(fs.readdir),
  // Recursively delete directory & contents
  deleteDir: promisify(rimraf),
}

Install mkdirp and rimraf npm packages for deleteDir & createDir

npm install mkdirp rimraf

Then you can use it in your project

const path = require('path')
const { fileExists, readFile } = require('./utils/fs')

async function doIt(filePath) {
  const exists = await fileExists(filePath)  
  let contents
  if (exists) {
    contents = await readFile(filePath)
  }
  return contents
}

const file = path.resolve('foo-bar.json')
doIt(file).then((contents) => {
  console.log('Yay 🎉', contents)
})

Hope this helps!

Let me know if you have other file system utilities you like to use in the comments below.

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Promisified node.js file system utilities

David Wells

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