I don't get it. JSON+LD is not Javascript. It's not even spelled the same? If you are meaning that your Javascript is able to read JSON+LD, so too could you WASM in this hypothetical world we're talking about.
Which, humorously, isn't compatible with Javascript object notation. { foo: "bar" } is a valid Javascript object, but not valid JSON.
Regardless, I don't get what you are trying to say. Pretty much every language still in existence is able to work with JSON (even SQL!). JSON is not Javascript. It's not clear why moving code from the Javascript runtime to the WASM runtime would magically make JSON+LD inoperable or whatever it is you are trying to say.
