Bytenode

A minimalist bytecode compiler for Node.js.

This tool truly compiles your JavaScript code into V8 bytecode, so that you can protect your source code. It can be used with Node.js, as well as Electron and NW.js (check examples/ directory).

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Install

npm install --save bytenode

Or globally:

sudo npm install -g bytenode

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Known Issues and Limitations

• In Node 10.x, Bytenode does not work in debug mode. See #29.

• Any code depends on Function.prototype.toString function will break, because Bytenode removes the source code from .jsc files and puts a dummy code instead. See #34. For a workaround, see #163

• Async Arrow Functions (and Arrow Functions in general) cause crashes in Puppeteer and in Electron apps. See #106, #47. They also cause issues with the ndb debugger. See #135. It seems that whenever there is a context change (or even when called from another file or module), arrow functions break because V8 inspects them internally using Function.prototype.toString in these cases. See #157.

• Electron ≥ 42 (V8 ≥ 14.8): bytecode compiled via ELECTRON_RUN_AS_NODE crashes the main process with SIGTRAP. V8's serialized bytecode header carries a read-only snapshot checksum (header offset 16). The Electron main/browser process boots V8 from Chromium's v8_context_snapshot, whose read-only heap differs from the Node default snapshot used by ELECTRON_RUN_AS_NODE. So a .jsc produced with compileElectronCode() (run-as-node) carries a checksum that does not match the main process. Starting with V8 14.8 this no longer fails gracefully (cachedDataRejected) but hard-aborts (EXC_BREAKPOINT / SIGTRAP) while deserializing. The fix is to compile in the same process type that will load the .jsc — use compileElectronMainCode() or compileFile({ electronMain: true }), which compile inside an actual Electron main process. (On Electron ≤ 41 / V8 ≤ 14.6 the two checksums happened to be compatible, so electron: true worked there.)

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Resources

• How To Compile Node.js Code Using Bytenode
• Bytenode Webpack Plugin
• Creating JS Binaries For Electron
• Electron Bytenode Example

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Bytenode CLI

  Usage: bytenode [option] [ FILE... | - ] [arguments]

  Options:
    -h, --help                        show help information.
    -v, --version                     show bytenode version.

    -c, --compile [ FILE... | - ]     compile stdin, a file, or a list of files
    --compress                        compress bytecode
    -n, --no-module                   compile without producing commonjs module
    -e, --electron                    compile for Electron
    -ep, --electron-path              path to Electron executable

    -l, --loader [ FILE | PATTERN ]   create a loader file and optionally define
                                      loader filename or pattern using % as
                                      filename replacer
                                      defaults to %.loader.js
    --no-loader                       do not create a loader file, conflicts
                                      with -l
    -t, --loader-type type            create a loader file of type commonjs or
                                      module. Defaults to CommonJS

  Examples:

  $ bytenode -c script.js             compile `script.js` to `script.jsc`.
  $ bytenode -c server.js app.js
  $ bytenode -c src/*.js              compile all `.js` files in `src/` directory.

  $ bytenode -c *.js -l %.load.js     create `filename.load.js` loader files along side `.jsc` files

  $ bytenode script.jsc [arguments]   run `script.jsc` with arguments.
  $ bytenode                          open Node REPL with bytenode pre-loaded.

Examples:

• Compile express-server.js to express-server.jsc.

user@machine:~$ bytenode --compile express-server.js

• Run your compiled file express-server.jsc.

user@machine:~$ bytenode express-server.jsc
Server listening on port 3000

• Compile all .js files in ./app directory.

user@machine:~$ bytenode --compile ./app/*.js

• Compile all .js files in your project.

user@machine:~$ bytenode --compile ./**/*.js

Note: you may need to enable globstar option in bash (you should add it to ~/.bashrc): shopt -s globstar

• Starting from v1.0.0, bytenode can compile from stdin.

echo 'console.log("Hello");' | bytenode --compile - > hello.jsc

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Bytenode API

const bytenode = require('bytenode');

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bytenode.compileCode(javascriptCode) → {Buffer}

Generates v8 bytecode buffer.

• Parameters:

Name	Type	Description
javascriptCode	string	JavaScript source that will be compiled to bytecode.

• Returns:

{Buffer} The generated bytecode.

• Example:

let helloWorldBytecode = bytenode.compileCode(
  `console.log('Hello World!');
  43;  // this will be returned`
);

This helloWorldBytecode bytecode can be saved to a file. However, if you want to use your code as a module (i.e. if your file has some exports), you have to compile it using bytenode.compileFile({compileAsModule: true}), or wrap your code manually, using Module.wrap() function.

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bytenode.compileElectronCode(javascriptCode, options) → {Promise\<Buffer>}

Asynchronous function which generates v8 bytecode buffer for Electron.

Same as bytenode.compileCode(), but generates bytecode for the version of Electron currently installed in node_modules.

• Parameters:

Name	Type	Description
javascriptCode	string	JavaScript source that will be compiled to bytecode.
options	object	Options object.
options.electronPath	string	Path to Electron executable.

• Returns:

{Promise\<Buffer>} A Promise which resolves with the generated bytecode.

• Example:

let helloWorldBytecode = await bytenode.compileElectronCode(
  `console.log('Hello World!');
  43;  // this will be returned`
);

This helloWorldBytecode bytecode can be saved to a file. However, if you want to use your code as a module (i.e. if your file has some exports), you have to compile it using bytenode.compileFile({compileAsModule: true}), or wrap your code manually, using Module.wrap() function.

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bytenode.compileElectronMainCode(javascriptCode, options) → {Promise\<Buffer>}

Asynchronous function which generates v8 bytecode buffer by compiling inside an actual Electron main process (NOT ELECTRON_RUN_AS_NODE).

Use this instead of compileElectronCode() when the .jsc will be loaded from the Electron main process on Electron ≥ 42 (V8 ≥ 14.8). Because the main process boots V8 from Chromium's v8_context_snapshot, the bytecode's read-only snapshot checksum only matches the runtime when it is produced in the same process type. Compiling via run-as-node there leads to a SIGTRAP crash at load time (see Known Issues).

It briefly launches Electron (no window is created) to compile, then exits.

CI / build environment notes

Because this spawns the Electron browser binary (not Node), the build machine must be able to run Electron: * macOS / Windows runners (e.g. GitHub Actions macos-*, windows-*): work out of the box. * Linux runners: Electron needs a display, so run the build under a virtual framebuffer, e.g. xvfb-run -a <build command> (install xvfb and the usual Electron shared libs: libgtk-3-0, libnss3, libasound2, …). Headless containers without xvfb will fail. * Running as root in a container: handled automatically — the compile launches Electron with --no-sandbox (no renderer is created, so the sandbox is unnecessary). * The spawned Electron must be the same version that will run the app (it is, when resolved from your project's node_modules), so the read-only snapshot checksum matches. * Cross-compiling bytecode for another OS/arch is not possible here — the .jsc must be produced by the Electron build for the target platform. Compile each platform on its own runner.

• Parameters:

Name	Type	Description
javascriptCode	string	JavaScript source that will be compiled to bytecode.
options	object	Options object.
options.electronPath	string	Path to Electron executable. Defaults to the electron binary resolved from node_modules.
options.compress	boolean	If true, compress the output bytecode with Brotli.

• Returns:

{Promise\<Buffer>} A Promise which resolves with the generated bytecode.

• Example:

let helloWorldBytecode = await bytenode.compileElectronMainCode(
  `console.log('Hello World!');
  43;  // this will be returned`
);

---

bytenode.runBytecode(bytecodeBuffer) → {any}

Runs v8 bytecode buffer and returns the result.

• Parameters:

Name	Type	Description
bytecodeBuffer	Buffer	The buffer object that was created using compileCode function.

• Returns:

{any} The result of the very last statement executed in the script.

• Example:

const result = bytenode.runBytecode(helloWorldBytecode);
// prints: Hello World!
console.log(result)
// prints: 43

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bytenode.compileFile(args, output) → {Promise\<string>}

Asynchronous function which compiles JavaScript file to .jsc file.

• Parameters:

Name	Type	Description
args	object | string
args.filename	string	The JavaScript source file that will be compiled.
args.compileAsModule	boolean	If true, the output will be a commonjs module. Default: true.
args.electron	boolean	If true, the output will be compiled through Electron via ELECTRON_RUN_AS_NODE. Default: false.
args.electronMain	boolean	If true, compile inside an actual Electron main process instead of ELECTRON_RUN_AS_NODE. Required for Electron ≥ 42 (V8 ≥ 14.8) when the .jsc is loaded from the main process. See Known Issues. Default: false.
args.electronPath	string	Path to Electron executable. Default: Electron binary from node_modules.
args.output	string	The output filename. Defaults to the same path and name of the original file, but with .jsc extension.
args.createLoader	boolean | string	If true, create a CommonJS loader file. As a string, select between module or commonjs loader. Default: false
args.loaderFilename	string	Filename or pattern for generated loader files. Defaults to originalFilename.loader.js. Use % as a substitute for originalFilename.
output	string	The output filename. (Deprecated: use args.output instead)

• Returns:

{Promise\<string>}: A Promise that resolves as the compiled filename.

• Examples:

let compiledFilename = bytenode.compileFile({
  filename: '/path/to/your/file.js',
  output: '/path/to/compiled/file.jsc' // if omitted, it defaults to '/path/to/your/file.jsc'
});

Previous code will produce a commonjs module that can be required using require function.

let compiledFilename = await bytenode.compileFile({
  filename: '/path/to/your/file.js',
  output: '/path/to/compiled/file.jsc',
  compileAsModule: false
});

Previous code will produce a direct .jsc file, that can be run using bytenode.runBytecodeFile() function. It can NOT be required as a module. Please note that compileAsModule MUST be false in order to turn it off. Any other values (including: null, "", etc) will be treated as true. (It had to be done this way in order to keep the old code valid.)

For Electron apps, compile through Electron so the bytecode matches Electron's V8. On Electron ≥ 42 (V8 ≥ 14.8) you must compile in the main process:

let compiledFilename = await bytenode.compileFile({
  filename: '/path/to/your/main.js',
  output: '/path/to/compiled/main.jsc',
  electronMain: true // Electron main-process compile (Electron >= 42 / V8 >= 14.8)
  // electron: true  // legacy ELECTRON_RUN_AS_NODE compile (Electron <= 41)
});

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bytenode.runBytecodeFile(filename) → {any}

Runs .jsc file and returns the result.

• Parameters:

Name	Type
filename	string

• Returns:

{any} The result of the very last statement executed in the