No, the language did not handle it fine. It allowed an invalid Unicode string to exist. This is basically a UTF-16 affliction—nothing that does UTF-16 validates, whereas almost everything that does UTF-8 does validate. encodeURIComponent deals with UTF-8, so of course it throws.

I'm realizing `encodeURIComponent` is actually part of the ECMA spec! I thought it was something provided by the browser like `window` or `document`. I withdraw my "the language handled it fine" comment, haha.

Before I'd looked that up I was going to say: I feel like "don't allow an invalid Unicode string to exist all" feels like a separate/bigger problem to me from "handling it fine" when they do get created. To the extent I can hand JavaScript an invalid combination of code units in a variety of other scenarios, returning a � felt fine.

e.g. // valid String.fromCodePoint(0xd83e, 0xdd20) // invalid, but "�" is ... fine? String.fromCodePoint(0xdd20, 0xd83e)