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Better file system API for Node.js

2 years after

fs-jetpack Build Status Build status

Node's fs library is very low level and because of that often painful to use. fs-jetpack wants to fix that by giving you completely rethought, much more convenient API to work with file system.

Jump to API Docs


npm install fs-jetpack


var jetpack = require('fs-jetpack');

What's cool about jetpack?

Promises instead of callbacks

API has the same set of synchronous and asynchronous methods. All async methods are promise based.

Commonly used naming convention in Node world is reversed in this library (no 'method' and 'methodSync' naming). Asynchronous methods are those with 'Async' suffix, all methods without 'Async' in the name are synchronous. Reason behind this is that it gives very nice look to blocking API, and promise based non-blocking code is verbose anyway, so one more word is not much of a difference.

Thanks to that the API is also coherent...

// If method has no 'Async' suffix it gives you answer right away.
var data = jetpack.read('file.txt');

// Want to make that call asynchronous? Just add the word "Async"
// and it will give you promise instead of ready value.
.then(function (data) {

Every jetpack instance has its internal CWD

You can create many jetpack objects with different internal working directories (which are independent of process.cwd()) and work on directories in a little more object-oriented manner.

var src = jetpack.cwd('path/to/source');
var dest = jetpack.cwd('path/to/destination');
src.copy('foo.txt', dest.path('bar.txt'));

JSON is a first class citizen

You can write JavaScript object directly to disk and it will be transformed to JSON automatically.

var obj = { greet: "Hello World!" };
jetpack.write('file.json', obj);

Then you can get your object back just by telling read method that it's a JSON.

var obj = jetpack.read('file.json', 'json');

Throws errors at you as the last resort

Everyone who did something with files for sure seen (and probably hates) "ENOENT, no such file or directory" error. Jetpack tries to recover from that error if possible.

  1. For write/creation operations, if any of parent directories doesn't exist jetpack will just create lacking directories.
  2. For read/inspect operations, if file or directory doesn't exist undefined is returned instead of throwing.

All methods play nicely with each other (examples)

Note: All examples are synchronous. Unfortunately asynchronous equivalents won't be that pretty.

Great for build scripts

var src = jetpack.cwd('path/to/source');
var dest = jetpack.dir('path/to/destination', { empty: true });

src.copy('.', dest.path(), {
    matching: ['./vendor/**', '*.html', '*.png', '*.jpg']

var config = src.read('config.json', 'json');
config.env = 'production';
dest.write('config.json', config);

Files creation in declarative style

Let's say you want to create folder structure:

|- greets
   |- greet.txt
   |- greet.json
|- greets-i18n
   |- polish.txt

Peace of cake with jetpack!

    .file('greet.txt', { content: 'Hello world!' })
    .file('greet.json', { content: { greet: 'Hello world!' } })
    .file('polish.txt', { content: 'Witaj świecie!' });

Delete all tmp files inside directory tree

jetpack.find('my-dir', {
    matching: '*.tmp'

Check if two files have the same content

var file1 = jetpack.inspect('file1', { checksum: 'md5' });
var file2 = jetpack.inspect('file2', { checksum: 'md5' });
var areTheSame = (file1.md5 === file2.md5);

API Docs

API methods have blocking and non-blocking equivalents:

// Synchronous call
var data = jetpack.read('file.txt');

// Asynchronous call
.then(function (data) {


append(path, data, [options])

asynchronous: appendAsync(path, data, [options])

Appends given data to the end of file. If file (or any parent directory) doesn't exist, creates it (or them).

path the path to file.
data data to append (could be String or Buffer).
options (optional) Object with possible fields:

  • mode if the file doesn't exist yet, will be created with given mode. Value could be number (eg. 0700) or string (eg. '700').


copy(from, to, [options])

asynchronous: copyAsync(from, to, [options])

Copies given file or directory (with everything inside).

from path to location you want to copy.
to path to destination location, where the copy should be placed.
options (optional) additional options for customization. Is an Object with possible fields:

  • overwrite (default: false) Whether to overwrite destination path if it exists. For directories, source directory is merged with destination directory, so files in destination which are not present in the source, will remain intact.
  • matching if defined will actually copy only items matching any of specified glob patterns and omit everything else (see examples below).



// Copies a file (and replaces it if one already exists in 'copied' directory)
jetpack.copy('file.txt', 'copied/file.txt', { overwrite: true });

// Copies only .md files inside 'dir' to 'copied-dir'
jetpack.copy('dir', 'copied-dir', { matching: '*.md' });

// Can add many globs as an array
jetpack.copy('dir', 'copied-dir', { matching: ['*.md', '*.txt'] });

// Supports negation patterns as well
jetpack.copy('dir', 'copied-dir', { matching: ['*.md', '!top-secret.md'] });

// All patterns are anchored to dir you want to copy, not to CWD.
// So in this example directory 'dir1/dir2/images' will be copied
// to 'copied-dir2/images'
jetpack.copy('dir1/dir2', 'copied-dir2', {
    matching: 'images/**'

createReadStream(path, [options])

Just an alias to vanilla fs.createReadStream.

createWriteStream(path, [options])

Just an alias to vanilla fs.createWriteStream.


Returns Current Working Directory (CWD) for this instance of jetpack, or creates new jetpack object with given path as its internal CWD.
Note: fs-jetpack never changes value of process.cwd(), the CWD we are talking about here is internal value inside every jetpack instance.

path... (optional) path (or many path parts) to become new CWD. Could be absolute, or relative. If relative path given new CWD will be resolved basing on current CWD of this jetpack instance.

If path not specified, returns CWD path of this jetpack object. For main instance of fs-jetpack it is always process.cwd().
If path specified, returns new jetpack object (totally the same thing as main jetpack). The new object resolves paths according to its internal CWD, not the global one (process.cwd()).


// Let's assume that process.cwd() outputs...
console.log(process.cwd()); // '/one/two/three'
// jetpack.cwd() will always return the same value as process.cwd()
console.log(jetpack.cwd()); // '/one/two/three'

// Now let's create new CWD context...
var jetParent = jetpack.cwd('..');
console.log(jetParent.cwd()); // '/one/two'
// ...and use this new context.
jetParent.dir('four'); // we just created directory '/one/two/four'

// One CWD context can be used to create next CWD context.
var jetParentParent = jetParent.cwd('..');
console.log(jetParentParent.cwd()); // '/one'

// When many parameters specified they are treated as parts of path to resolve
var sillyCwd = jetpack.cwd('a', 'b', 'c');
console.log(sillyCwd.cwd()); // '/one/two/three/a/b/c'

dir(path, [criteria])

asynchronous: dirAsync(path, [criteria])

Ensures that directory on given path exists and meets given criteria. If any criterium is not met it will be after this call.

path path to directory to examine.
criteria (optional) criteria to be met by the directory. Is an Object with possible fields:

  • empty (default: false) whether directory should be empty (no other files or directories inside). If set to true and directory contains any files or subdirectories all of them will be deleted.
  • mode ensures directory has specified mode. If not set and directory already exists, current mode will be preserved. Value could be number (eg. 0700) or string (eg. '700').

New CWD context with directory specified in path as CWD.


// Creates directory if doesn't exist

// Makes sure directory mode is 0700 and that it's empty
jetpack.dir('empty-dir', { empty: true, mode: '700' });

// Because dir returns new CWD context pointing to just
// created directory you can create dir chains.
.dir('main-dir') // creates 'main-dir'
.dir('sub-dir'); // creates 'main-dir/sub-dir'


asynchronous: existsAsync(path)

Checks whether something exists on given path. This method returns values more specific than true/false to protect from errors like "I was expecting directory, but it was a file".


  • false if path doesn't exist.
  • "dir" if path is a directory.
  • "file" if path is a file.
  • "other" if none of the above.

file(path, [criteria])

asynchronous: fileAsync(path, [criteria])

Ensures that file exists and meets given criteria. If any criterium is not met it will be after this call.

path path to file to examine.
criteria (optional) criteria to be met by the file. Is an Object with possible fields:

  • content sets file content. Could be String, Buffer, Object or Array. If Object or Array given to this parameter data will be written as JSON.
  • jsonIndent (defaults to 2) if writing JSON data this tells how many spaces should one indentation have.
  • mode ensures file has specified mode. If not set and file already exists, current mode will be preserved. Value could be number (eg. 0700) or string (eg. '700').

Jetpack object you called this method on (self).


// Creates file if doesn't exist

// Creates file with mode '777' and content 'Hello World!'
jetpack.file('hello.txt', { mode: '777', content: 'Hello World!' });

find([path], searchOptions)

asynchronous: findAsync([path], searchOptions)

Finds in directory specified by path all files fulfilling searchOptions. Returned paths are relative to current CWD of jetpack instance.

path (optional, defaults to '.') path to start search in (all subdirectories will be searched).
searchOptions is an Object with possible fields:

  • matching glob patterns of files you would like to find.
  • files (default true) whether or not should search for files.
  • directories (default false) whether or not should search for directories.

Array of found files.


// Finds all files which has 2015 in the name
jetpack.find('my-work', { matching: '*2015*' });

// Finds all .js files inside 'my-project' but excluding those in 'vendor' subtree.
jetpack.find('my-project', { matching: ['*.js', '!vendor/**/*'] });

// Looks for all directories named 'foo' (and will omit all files named 'foo').
jetpack.find('my-work', { matching: ['foo'], files: false, directories: true });

// Path parameter might be omitted and CWD is used as path in that case.
var myStuffDir = jetpack.cwd('my-stuff');
myStuffDir.find({ matching: ['*.md'] });

inspect(path, [options])

asynchronous: inspectAsync(path, [options])

Inspects given path (replacement for fs.stat). Returned object by default contains only very basic, not platform-dependent properties (so you have something e.g. your unit tests can rely on), you can enable more properties through options object.

path path to inspect.
options (optional). Possible values:

  • checksum if specified will return checksum of inspected file. Possible values are strings 'md5', 'sha1' or 'sha256'. If given path is directory this field is ignored.
  • mode (default false) if set to true will add file mode (unix file permissions) value.
  • times (default false) if set to true will add atime, mtime and ctime fields (here called accessTime, modifyTime and changeTime).
  • absolutePath (default false) if set to true will add absolute path to this resource.
  • symlinks (default false) if set to true will just inspect symlink itself and not follow it.

returns: undefined if given path doens't exist.
Otherwise Object of structure:

    name: "my_dir",
    type: "file", // possible values: "file", "dir"
    size: 123, // size in bytes, this is returned only for files
    // if checksum option was specified:
    md5: '900150983cd24fb0d6963f7d28e17f72',
    // if mode option was set to true:
    mode: 33204,
    // if times option was set to true:
    accessTime: [object Date],
    modifyTime: [object Date],
    changeTime: [object Date]

inspectTree(path, [options])

asynchronous: inspectTreeAsync(path, [options])

Calls inspect recursively on given path so it creates tree of all directories and sub-directories inside it.

path the path to inspect.
options (optional). Possible values:

  • checksum if specified will also calculate checksum of every item in the tree. Possible values are strings 'md5', 'sha1' or 'sha256'. Checksums for directories are calculated as checksum of all children' checksums plus their filenames (see example below).
  • relativePath if set to true every tree node will have relative path anchored to root inspected folder.

undefined if given path doesn't exist. Otherwise tree of inspect objects like:

    name: 'my_dir',
    type: 'dir',
    size: 123, // this is combined size of all items in this directory
    relativePath: '.',
    md5: '11c68d9ad988ff4d98768193ab66a646',
    // checksum of this directory was calculated as:
    // md5(child[0].name + child[0].md5 + child[1].name + child[1].md5)
    children: [
            name: 'empty',
            type: 'dir',
            size: 0,
            relativePath: './dir',
            md5: 'd41d8cd98f00b204e9800998ecf8427e',
            children: []
            name: 'file.txt',
            type: 'file',
            size: 123,
            relativePath: './file.txt',
            md5: '900150983cd24fb0d6963f7d28e17f72'


asynchronous: listAsync(path)

Lists the contents of directory. Equivalent of fs.readdir.

path (optional) path to directory you would like to list. If not specified defaults to CWD.

Array of file names inside given path, or undefined if given path doesn't exist.

move(from, to)

asynchronous: moveAsync(from, to)

Moves given path to new location.

from path to directory or file you want to move.
to path where the thing should be moved.



Returns path resolved to internal CWD of this jetpack object.

parts strings to join and resolve as path (as many as you like).

Resolved path as string.


jetpack.cwd(); // if it returns '/one/two'
jetpack.path(); // this will return the same '/one/two'
jetpack.path('three'); // this will return '/one/two/three'
jetpack.path('..', 'four'); // this will return '/one/four'

read(path, [returnAs])

asynchronous: readAsync(path, [returnAs])

Reads content of file.

path path to file.
returnAs (optional) how the content of file should be returned. Is a string with possible values:

  • 'utf8' (default) content will be returned as UTF-8 String.
  • 'buffer' content will be returned as a Buffer.
  • 'buf' deprecated use 'buffer' instead.
  • 'json' content will be returned as parsed JSON object.
  • 'jsonWithDates' content will be returned as parsed JSON object, and date strings in ISO format will be automatically turned into Date objects.

File content in specified format, or undefined if file doesn't exist.


asynchronous: removeAsync([path])

Deletes given path, no matter what it is (file or directory). If path already doesn't exist ends without throwing, so you can use it as 'ensure path doesn't exist'.

path (optional) path to file or directory you want to remove. If not specified the remove action will be performed on current working directory (CWD).



// Deletes file

// Deletes directory "important_stuff" and everything inside

// Remove can be called with no parameters and will default to CWD then.
// In this example folder 'my_work' will cease to exist.
var myStuffDir = jetpack.cwd('my_stuff');

rename(path, newName)

asynchronous: renameAsync(path, newName)

Renames given file or directory.

path path to thing you want to change name.
newName new name for this thing (not full path, just a name).


symlink(symlinkValue, path)

asynchronous: symlinkAsync(symlinkValue, path)

Creates symbolic link.

symlinkValue path where symbolic link should point.
path path where symbolic link should be put.


write(path, data, [options])

asynchronous: writeAsync(path, data, [options])

Writes data to file.

path path to file.
data data to be written. This could be String, Buffer, Object or Array (if last two used, the data will be outputted into file as JSON).
options (optional) Object with possible fields:

  • atomic (default false) if set to true the file will be written using strategy which is much more resistant to data loss. The trick is very simple, read this to get the concept.
  • jsonIndent (defaults to 2) if writing JSON data this tells how many spaces should one indentation have.


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