Node 21 Release Highlights!

Another Node.js version has just been released! Let’s talk about the major features in this new release.

Remember that odd-numbered releases are not recommended for production, but rather experimental releases so you can test and give feedback to the community!

Currently we’re on version 20 until October next year, Node 21 will be available until April 2024, and then we’ll have version 22 which will be the new LTS version!

Native WebSockets#

Version 21 starts with a very welcome feature! An implementation compatible with browser WebSockets was added in the new release as an experimental flag. To use it, just start your application with the --experimental-websocket flag.

Currently the implementation allows opening and closing connections, as well as sending data. It provides four events: open, close, message, and error. This is great because soon we won’t need to rely on implementations like Socket.io to make applications communicate over bidirectional channels.¹

More information is available in the MDN documentation.

Array grouping#

With the inclusion of V8 version 11.8, we now have the array grouping methods. I’ve already written about them before here on the blog, but there was a small change to the API. Instead of being a method on the array prototype, groupBy is now a static method that can be used like this:

1
const array = [1, 2, 3, 4, 5];
2

3
Object.groupBy(array, (num, index) => {
4
  return num % 2 === 0 ? 'par': 'impar';
5
});
6
// =>  { impar: [1, 3, 5], par: [2, 4] }

The same applies to maps, the difference is that the result will be returned in a Map by key, which is useful for grouping items by a key from some object:

1
const par  = { odd: true };
2
const impar = { even: true };
3
Map.groupBy(array, (num, index) => {
4
  return num % 2 === 0 ? par: impar;
5
});
6
// =>  Map { {odd: true}: [1, 3, 5], {even: true}: [2, 4] }

writeFile Flush#

The addition of a new property called { flush: true } to the writeFile function now allows you to force data being written to a file to be written directly after a successful write.

This feature was added because in some cases, when reading a file, the read operation could get stale data that hadn’t been written yet due to the asynchronous nature of write operations.

Now these functions:

• fileHandle.createWriteStream
• fsPromises.writeFile
• fs.createWriteStream
• fs.writeFile
• fs.writeFileSync

All can receive a property in the options object with { flush: true }, but it’s not enabled by default.

Adding window.navigator#

This release also includes a global object called navigator that is identical to the window.navigator we have in browsers. Node is increasingly moving toward direct compatibility with the web and browsers.

For now, navigator doesn’t have much yet, but this opens the door for other properties to be added in the future.

Automatic module detection#

A new flag called --experimental-detect-module was added and can be used to automatically detect whether a file is CommonJS or ESM. Finally, we don’t need to identify the module type in our package.json anymore.

But be careful, this flag causes a slower startup than usual, so if you maintain a library, it’s still recommended to include type: module in your package.json because that way the application startup can be faster since Node won’t need to check the module type.

Other changes#

• Fetch and WebStreams are now stable!
• Performance improvements
• Addition of the --experimental-default-type flag that allows changing the default module type to ESM (no longer need type: module in package.json)
• The test runner now supports globs