Some example of pure JavaScript implementations are:
http://viejs.org/ ,
http://www.hydra-cg.com/
Of course, SPARQL servers can spit JSON-LD, which can readily be used by many JS libraries. An idea is to leverage on Angular.js to achieve automatic update of forms when the local JS model changes.
A JavaScript library usable for RDF (actually used by Stample project): https://github.com/linkeddata/rdflib.js