v8flags

What is v8flags?

The v8flags npm package is used to fetch the flags available for the V8 JavaScript engine that Node.js runs on. It provides an API to programmatically access the list of V8 command-line flags, which can be useful for tools that spawn child processes of Node.js and need to pass flags to the V8 engine.

What are v8flags's main functionalities?

Fetching V8 flags

This feature allows you to fetch the available V8 flags for the current version of Node.js. The flags are returned as an array of strings, each representing a command-line flag that can be used with V8.

const v8flags = require('v8flags');
v8flags.then(flags => console.log(flags));

Caching V8 flags

v8flags caches the flags to a file to avoid the performance cost of spawning a new process on subsequent calls. You can specify a custom cache directory by configuring the package.

const v8flags = require('v8flags');
v8flags.config({
  cacheDir: '/path/to/cache/directory'
});
v8flags.then(flags => console.log(flags));

Other packages similar to v8flags

minimist

Minimist is a package that helps parse argument options, which is somewhat related to v8flags in that it deals with command-line arguments. However, minimist does not provide a list of V8 flags; it simply parses the arguments passed to a script.

commander

Commander is a complete solution for node.js command-line interfaces, which includes parsing user-supplied command-line options. While it does not provide V8 flags, it is used for a similar purpose of handling command-line arguments.

yargs

Yargs is another node.js library for building command-line tools, which parses command-line arguments and generates an elegant user interface. It's similar to v8flags in that it deals with command-line options but does not specifically provide V8 flags.

README

v8flags

Get available v8 flags.

Example

const v8flags = require('v8flags');

v8flags(function (err, results) {
  console.log(results);  // [ '--use_strict',
                         //   '--es5_readonly',
                         //   '--es52_globals',
                         //   '--harmony_typeof',
                         //   '--harmony_scoping',
                         //   '--harmony_modules',
                         //   '--harmony_proxies',
                         //   '--harmony_collections',
                         //   '--harmony',
                         // ...
});

Release History

• 2015-06-15 - v2.0.6 - store cache file in ~/.cache or ~/AppData/Local depending on platform
• 2015-04-18 - v2.0.5 - attempt to require config file, if this throws for any reason, fopen w+ and re-create
• 2015-04-16 - v2.0.4 - when concurrent processes are run and no config exists, don't append to the cached config.
• 2015-03-31 - v2.0.3 - prefer to store config files in user home over tmp
• 2015-01-18 - v2.0.2 - keep his dark tentacles contained
• 2015-01-15 - v2.0.1 - store temp file in os.tmpdir(), drop support for node 0.8
• 2015-01-15 - v2.0.0 - make the stupid thing async
• 2014-12-22 - v1.0.8 - exclude --help flag
• 2014-12-20 - v1.0.7 - pre-cache flags for every version of node from 0.8 to 0.11
• 2014-12-09 - v1.0.6 - revert to 1.0.0 behavior
• 2014-11-26 - v1.0.5 - get node executable from process.execPath
• 2014-11-18 - v1.0.4 - wrap node executable path in quotes
• 2014-11-17 - v1.0.3 - get node executable during npm install via process.env.NODE
• 2014-11-17 - v1.0.2 - get node executable from process.env._
• 2014-09-03 - v1.0.0 - first major version release
• 2014-09-02 - v0.3.0 - keep -- in flag names
• 2014-09-02 - v0.2.0 - cache flags
• 2014-05-09 - v0.1.0 - initial release