[twiss]

For a more authoritative reference, the WebIDL spec explains: (https://webidl.spec.whatwg.org/#idl-objects)

> the browser-implemented DOM objects (implementing interfaces such as Node and Document) that provide access to a web page’s contents to JavaScript running in the page would be platform objects. These objects might be exotic objects, implemented in a language like C++, or they might be native JavaScript objects. Regardless, an implementation of a given set of IDL fragments needs to be able to recognize all platform objects that are created by the implementation. This might be done by having some internal state that records whether a given object is indeed a platform object for that implementation, or perhaps by observing that the object is implemented by a given internal C++ class. How exactly platform objects are recognized by a given implementation of a set of IDL fragments is implementation specific.