Sure, but then why would you use Javascript in the first place? The situation deno is trying to address is that JS developers need to memorize two standard libraries, one for browsers and one for node. You should be able to work with one standard library like you can in most other languages.

The first attempt at this was to port the node standard library to the browser via browserify and the like. This tended to create gigantic JS build artifacts and frequently led to runtime errors when developers used an abstraction that just had no equivalent in the browser (like saving something to disk or opening a separate process). The browser is definitely the lowest common denominator of JS runtimes, even if there are a few browser APIs that just don't make sense in a server environment (like window.history)