Node.js: fs-extra

fs-extra adds file system methods that aren't included in the native fs module. It is a drop in replacement for fs.

Why?

I got tired of including mkdirp, rimraf, and ncp in most of my projects.

Installation

npm install --save fs-extra

Usage

fs-extra is a drop in replacement for native fs. All methods in fs are unmodified and attached to fs-extra.

You don't ever need to include the original fs module again:

const fs = require('fs') // this is no longer necessary

you can now do this:

const fs = require('fs-extra')

or if you prefer to make it clear that you're using fs-extra and not fs, you may want to name your fs variable fse like so:

const fse = require('fs-extra')

you can also keep both, but it's redundant:

const fs = require('fs')
const fse = require('fs-extra')

Sync vs Async

Most methods are async by default (they take a callback with an Error as first argument).

Sync methods on the other hand will throw if an error occurs.

Example:

const fs = require('fs-extra')

fs.copy('/tmp/myfile', '/tmp/mynewfile', err => {
  if (err) return console.error(err)
  console.log("success!")
});

try {
  fs.copySync('/tmp/myfile', '/tmp/mynewfile')
  console.log("success!")
} catch (err) {
  console.error(err)
}

Methods

• copy
• copySync
• emptyDir
• emptyDirSync
• ensureFile
• ensureFileSync
• ensureDir
• ensureDirSync
• ensureLink
• ensureLinkSync
• ensureSymlink
• ensureSymlinkSync
• mkdirs
• mkdirsSync
• move
• outputFile
• outputFileSync
• outputJson
• outputJsonSync
• readJson
• readJsonSync
• remove
• removeSync
• writeJson
• writeJsonSync

NOTE: You can still use the native Node.js methods. They are copied over to fs-extra.

What happened to walk() and walkSync()?

They were removed from fs-extra in v2.0.0. If you need the functionality, walk and walkSync are available as separate packages, klaw and klaw-sync.

Third Party

Promises

Use Bluebird. See https://github.com/petkaantonov/bluebird/blob/master/API.md#promisification. fs-extra is explicitly listed as supported.

const Promise = require('bluebird')
const fs = Promise.promisifyAll(require('fs-extra'))

Or you can use a dedicated package:

• fs-extra-promise uses Bluebird.
• fs-promise uses Any Promise and also covers mz/fs.
• fs-p - TypeScript-friendly promises implementation

TypeScript

If you like TypeScript, you can use fs-extra with it: https://github.com/borisyankov/DefinitelyTyped/tree/master/fs-extra

File / Directory Watching

If you want to watch for changes to files or directories, then you should use chokidar.

Misc.

• mfs - Monitor your fs-extra calls.

Hacking on fs-extra

Wanna hack on fs-extra? Great! Your help is needed! fs-extra is one of the most depended upon Node.js packages. This project uses JavaScript Standard Style - if the name or style choices bother you, you're gonna have to get over it :) If standard is good enough for npm, it's good enough for fs-extra.

What's needed?

• First, take a look at existing issues. Those are probably going to be where the priority lies.
• More tests for edge cases. Specifically on different platforms. There can never be enough tests.
• Improve test coverage. See coveralls output for more info.

Note: If you make any big changes, you should definitely file an issue for discussion first.

Running the Test Suite

fs-extra contains hundreds of tests.

• npm run lint: runs the linter (standard)
• npm run unit: runs the unit tests
• npm test: runs both the linter and the tests

Windows

If you run the tests on the Windows and receive a lot of symbolic link EPERM permission errors, it's because on Windows you need elevated privilege to create symbolic links. You can add this to your Windows's account by following the instructions here: http://superuser.com/questions/104845/permission-to-make-symbolic-links-in-windows-7 However, I didn't have much luck doing this.

Since I develop on Mac OS X, I use VMWare Fusion for Windows testing. I create a shared folder that I map to a drive on Windows. I open the Node.js command prompt and run as Administrator. I then map the network drive running the following command:

net use z: "\\vmware-host\Shared Folders"

I can then navigate to my fs-extra directory and run the tests.

Naming

I put a lot of thought into the naming of these functions. Inspired by @coolaj86's request. So he deserves much of the credit for raising the issue. See discussion(s) here:

• jprichardson#2
• flatiron/utile#11
• ryanmcgrath/wrench-js#29
• https://github.com/substack/node-mkdirp/issues/17

First, I believe that in as many cases as possible, the Node.js naming schemes should be chosen. However, there are problems with the Node.js own naming schemes.

For example, fs.readFile() and fs.readdir(): the F is capitalized in File and the d is not capitalized in dir. Perhaps a bit pedantic, but they should still be consistent. Also, Node.js has chosen a lot of POSIX naming schemes, which I believe is great. See: fs.mkdir(), fs.rmdir(), fs.chown(), etc.

We have a dilemma though. How do you consistently name methods that perform the following POSIX commands: cp, cp -r, mkdir -p, and rm -rf?

My perspective: when in doubt, err on the side of simplicity. A directory is just a hierarchical grouping of directories and files. Consider that for a moment. So when you want to copy it or remove it, in most cases you'll want to copy or remove all of its contents. When you want to create a directory, if the directory that it's suppose to be contained in does not exist, then in most cases you'll want to create that too.

So, if you want to remove a file or a directory regardless of whether it has contents, just call fs.remove(path). If you want to copy a file or a directory whether it has contents, just call fs.copy(source, destination). If you want to create a directory regardless of whether its parent directories exist, just call fs.mkdirs(path) or fs.mkdirp(path).

Credit

fs-extra wouldn't be possible without using the modules from the following authors:

• Isaac Shlueter
• Charlie McConnel
• James Halliday
• Andrew Kelley

License

Licensed under MIT

Copyright (c) 2011-2017 JP Richardson