>Those believe that it is somehow physically possible to engineer the language parser that it use some extremely sophisticated lexic tools to guess what version

>Those believe that it is somehow physically possible to engineer the language parser that it use some extremely sophisticated lexic tools to guess what version of JS something the code refers, those also are the proponents of "lets guess the api version by counting the number of arguments, and if we need a new one, we just add one more" You don't need that luckily, we have DOCTYPE to tell us something about the version of a document. A simple `<!DOCTYPE html js2018>` would be sufficient IMO though it might break older browser (but honestly, screw everyone still using IE8) On the other hand we have WASM now and once we get proper integration into browser I imagine things might get better.