FWIW, my last hack in rdfjs space is https://github.com/niklasl/ldtr It is sort of a "cheat", since it just transcribes TriG into JSON-LD. It might be interesting as a comparison to proper triple representations though (although it does hide the "true nature" of RDF).
@RubenVerborgh We're talking about an in-memory representation... there's several Turtle parsers, each of them outputs in different ways. What we're trying to achieve is a common data format for output
@Acubed: Its annotating the HTML forms with RDF specific markup (e.g. rex-subject, rex-predicate, ...) such that the form can be both pre-filled out from existing data in a sparql endpoint as well as persist any changes back to it