Chapter 2. Features

This release includes an upgrade of the V8 JavaScript engine to v10.2, which is part of Chromium 101.

The upgraded V8 JavaScript engine includes the following new features and enhancements:

For more information about the changes that are available in the V8 JavaScript Engine, see the V8 blog.

This release includes the following enhancements for HTTP timeouts:

If these timeouts expire, the server responds with a 408 error and closes the connection without forwarding the request to the request listener.

The following APIs are now fully supported and available as global objects:

In the previous release, these APIs were Technology Preview features only.

This release includes the runtime deprecation of implicit object-to-string coercion when an object has its own toString property that is passed as a parameter in any of the following methods:

As an alternative to string coercion, convert objects to primitive strings instead.

This release removes the coercion of option types that are passed as a parameter in the dns.lookup() and dnsPromises.lookup() methods. If you use any of the following combinations of option type and value, Node.js now throws an ERR_INVALID_ARG_TYPE error:

This release includes the runtime deprecation of the multipleResolves process event. For example:

process.on('multipleResolves', handler)

The multipleResolves event did not work with V8 promise combinators, which affected the usefulness and reliability of this event in tracking potential errors when using the Promise constructor. For example, the Promise.race() method could also trigger a multipleResolves event, which did not necessarily indicate an error.

This release removes the ability to return thenable objects in stream implementation methods. The use of thenable objects could lead to unexpected issues if, for example, a user implemented the function in callback style but used an async method. This type of implementation resulted in an invalid mix of promise and callback semantics.

For example:

const w = new Writable({
  async final(callback) {
    await someOp();
    callback();
  },
});

As an alternative to thenable objects, use callbacks instead and avoid using the async function for stream implementation methods.

This release removes the tls.parseCertString() method, which was a parser helper to parse the certificate subject and issuer strings. The tls.parseCertString() method did not handle multi-value Relative Distinguished Names (RDNs) correctly, which could lead to incorrect representations and security issues.

Additionally, _tls_common.translatePeerCertificate no longer translates the subject and issuer properties.

An experimental fetch API is available as a global object. The fetch API is based on Undici, which is an HTTP/1.1 client for Node.js, and the node-fetch module, which provides a Node.js implementation of the Fetch Web API.

For example:

const res = await fetch('https://nodejs.org/api/documentation.json');
if (res.ok) {
  const data = await res.json();
  console.log(data);
}

Because of this enhancement, the following global objects are now available for use:

You can disable the fetch API by using the --no-experimental-fetch command-line option.

The Web Streams API was introduced as a Technology Preview feature in the Red Hat build of Node.js 16 release. In this release, Node.js now exposes the Web Streams API in the global scope. This supersedes the behavior in the previous release where the Web Streams API was only accessible by using the stream/web core module.

Because of this enhancement, the following APIs are now available as global objects:

ReadableStream, ReadableStreamDefaultReader, ReadableStreamBYOBReader, ReadableStreamBYOBRequest, ReadableByteStreamController, ReadableStreamDefaultController, TransformStream, TransformStreamDefaultController, WritableStream, WritableStreamDefaultWriter, WritableStreamDefaultController, ByteLengthQueuingStrategy, CountQueuingStrategy, TextEncoderStream, TextDecoderStream, CompressionStream, DecompressionStream

The ESM Loader Hooks API was introduced as a Technology Preview feature in the Red Hat build of Node.js 16 release. The ESM Loader Hooks API now supports multiple custom loaders.

To enable multiple loaders to work together, this feature uses a process called chaining, which is analogous to a promise chain. For example, first-loader calls second-loader, second-loader calls third-loader, and so on.

For more information, see the Node.js ECMAScript modules documentation.

You can now run Node.js applications in watch mode by using the node --watch option.

Running an application in watch mode means that the process restarts if you modify an imported file.