NaCl is actually designed to interoperate with JS in a fairly rich way and this interoperability is designed to be provided entirely by the browser. The idea is

NaCl is actually designed to interoperate with JS in a fairly rich way and this interoperability is designed to be provided entirely by the browser. The idea is that you pick the runtime that you want -- probably the one provided by your browser -- and it pokes (hopefully secured) holes in the safe box that native client guarantees. This includes a sort of networking API that JS can call in to.