pkg: A JavaScript repository from luzlab

Disclaimer: pkg was created for use within containers and is not intended for use in serverless environments. For those using Vercel, this means that there is no requirement to use pkg in your projects as the benefits it provides are not applicable to the platform.

This command line interface enables you to package your Node.js project into an executable that can be run even on devices without Node.js installed.

Use Cases

Make a commercial version of your application without sources
Make a demo/evaluation/trial version of your app without sources
Instantly make executables for other platforms (cross-compilation)
Make some kind of self-extracting archive or installer
No need to install Node.js and npm to run the packaged application
No need to download hundreds of files via npm install to deploy your application. Deploy it as a single file
Put your assets inside the executable to make it even more portable
Test your app against new Node.js version without installing it

Usage

npm install -g pkg

After installing it, run pkg --help without arguments to see list of options.

The entrypoint of your project is a mandatory CLI argument. It may be:

Path to entry file. Suppose it is /path/app.js, then packaged app will work the same way as node /path/app.js
Path to package.json. Pkg will follow bin property of the specified package.json and use it as entry file.
Path to directory. Pkg will look for package.json in the specified directory. See above.

Targets

pkg can generate executables for several target machines at a time. You can specify a comma-separated list of targets via --targets option. A canonical target consists of 3 elements, separated by dashes, for example node6-macos-x64 or node4-linux-armv6:

nodeRange node${n} or latest
platform freebsd, linux, alpine, macos, win
arch x64, x86, armv6, armv7

You may omit any element (and specify just node6 for example). The omitted elements will be taken from current platform or system-wide Node.js installation (its version and arch). There is also an alias host, that means that all 3 elements are taken from current platform/Node.js. By default targets are linux,macos,win for current Node.js version and arch.

Config

During packaging process pkg parses your sources, detects calls to require, traverses the dependencies of your project and includes them into executable. In most cases you don't need to specify anything manually. However your code may have require(variable) calls (so called non-literal argument to require) or use non-javascript files (for example views, css, images etc).

  require('./build/' + cmd + '.js')
  path.join(__dirname, 'views/' + viewName)

Such cases are not handled by pkg. So you must specify the files - scripts and assets - manually in pkg property of your package.json file.

  "pkg": {
    "scripts": "build/**/*.js",
    "assets": "views/**/*"
  }

You may also specify arrays of globs:

    "assets": [ "assets/**/*", "images/**/*" ]

Just be sure to call pkg package.json or pkg . to make use of scripts and assets entries.

Scripts

scripts is a glob or list of globs. Files specified as scripts will be compiled using v8::ScriptCompiler and placed into executable without sources. They must conform to the JS standards of those Node.js versions you target (see Targets), i.e. be already transpiled.

Assets

assets is a glob or list of globs. Files specified as assets will be packaged into executable as raw content without modifications. Javascript files may also be specified as assets. Their sources will not be stripped as it improves execution performance of the files and simplifies debugging.

Options

Node.js application can be called with runtime options (belonging to Node.js or V8). To list them type node --help or node --v8-options. You can "bake" these runtime options into packaged application. The app will always run with the options turned on. Just remove -- from option name.

pkg app.js --options expose-gc
pkg app.js --options max_old_space_size=4096

Output

You may specify --output if you create only one executable or --out-path to place executables for multiple targets.

Debug

Pass --debug to pkg to get a log of packaging process. If you have issues with some particular file (seems not packaged into executable), it may be useful to look through the log.

Build

pkg has so called "base binaries" - they are actually same node executables but with some patches applied. They are used as a base for every executable pkg creates. pkg downloads precompiled base binaries before packaging your application. If you prefer to compile base binaries from source instead of downloading them, you may pass --build option to pkg. First ensure your computer meets the requirements to compile original Node.js: BUILDING.md

Usage of packaged app

Command line call to packaged app ./app a b is equivalent to node app.js a b

Snapshot filesystem

During packaging process pkg collects project files and places them into executable. It is called a snapshot. At run time the packaged application has access to snapshot filesystem where all that files reside.

Packaged files have /snapshot/ prefix in their paths (or C:\snapshot\ in Windows). If you used pkg /path/app.js command line, then __filename value will be likely /snapshot/path/app.js at run time. __dirname will be /snapshot/path as well. Here is the comparison table of path-related values:

value	with `node`	packaged	comments
__filename	/project/app.js	/snapshot/project/app.js
__dirname	/project	/snapshot/project
process.cwd()	/project	/deploy	suppose the app is called ...
process.execPath	/usr/bin/nodejs	/deploy/app-x64	`app-x64` and run in `/deploy`
process.argv[0]	/usr/bin/nodejs	/deploy/app-x64
process.argv[1]	/project/app.js	/snapshot/project/app.js
process.pkg.entrypoint	undefined	/snapshot/project/app.js
process.pkg.defaultEntrypoint	undefined	/snapshot/project/app.js
require.main.filename	/project/app.js	/snapshot/project/app.js

Hence, in order to make use of a file collected at packaging time (require a javascript file or serve an asset) you should take __filename, __dirname, process.pkg.defaultEntrypoint or require.main.filename as a base for your path calculations. For javascript files you can just require or require.resolve because they use current __dirname by default. For assets use path.join(__dirname, '../path/to/asset'). Learn more about path.join in Detecting assets in source code.

On the other hand, in order to access real file system at run time (pick up a user's external javascript plugin, json configuration or even get a list of user's directory) you should take process.cwd() or path.dirname(process.execPath).

Detecting assets in source code

When pkg encounters path.join(__dirname, '../path/to/asset'), it automatically packages the file specified as an asset. See Assets. Pay attention that path.join must have two arguments and the last one must be a string literal.

This way you may even avoid creating pkg config for your project.

Native addons

Native addons (.node files) use is supported. When pkg encounters a .node file in a require call, it will package this like an asset. In some cases (like with the bindings package), the module path is generated dynamicaly and pkg won't be able to detect it. In this case, you should add the .node file directly in the assets field in package.json.

The way NodeJS requires native addon is different from a classic JS file. It needs to have a file on disk to load it but pkg only generate one file. To circumvent this, pkg will create a temporary file on the disk. These files will stay on the disk after the process has exited and will be used again on the next process launch.

When a package, that contains a native module, is being installed, the native module is compiled against current system-wide Node.js version. Then, when you compile your project with pkg, pay attention to --target option. You should specify the same Node.js version as your system-wide Node.js to make compiled executable compatible with .node files.

API

const { exec } = require('pkg')

exec(args) takes an array of command line arguments and returns a promise. For example:

await exec([ 'app.js', '--target', 'host', '--output', 'app.exe' ])
// do something with app.exe, run, test, upload, deploy, etc

Troubleshooting

Error: ENOENT: no such file or directory, uv_chdir

This error can be caused by deleting the directory the application is run from. Or, generally, deleting process.cwd() directory when the application is running.

luzlab/pkg