> Exceptions are about control flow.
You're thinking of "try ... catch", but that's not what I'm talking about. What I'm talking about, and what I wrote, was "exceptions", i.e., objects that signify you're dealing with an exceptional case.
> Nulls and undefined are about types.
Anything that can be checked with instanceof, as I'm alluding to and as described in the first comment, or cross-checked by comparing a tag against constant, as in the case of node types in the DOM, is "about types".
What you describe as "just check[ing] if a value is an instance of InvalidType" is a straightforward restatement of how to represent an exception and handle it. Give it extra fields with further details, etc. This is widely used, it's just not widely used in in the NodeJS world, but that has more to do with the dubious influence that people like OP have, and all the programmers who try to emulate his style.
