A JSSClass represents a custom JavaScript class registered by the user in a #JSCContext.
It allows to create new JavaScripts objects whose instances are created by the user using
this API.
It’s possible to add constructors, properties and methods for a JSSClass by providing
#GCallbacks to implement them.
JSCVirtualMachine represents a group of JSCContexts. It allows
concurrent JavaScript execution by creating a different instance of
JSCVirtualMachine in each thread.
JSCWeakValue represents a weak reference to a value in a #JSCContext. It can be used
to keep a reference to a JavaScript value without protecting it from being garbage
collected and without referencing the #JSCContext either.