From: Brendan Eich [bren...@mozilla.com] > Yes, and I've written about why invariants matter on occasion -- perhaps you > missed that :-P.
Heh, 2008 was before my time. But generally yes, I certainly understand the importance of invariants. I am just not sure this particular invariant is something people actually depend on. This I guess is the heart of my question. When I said "nobody uses `==`," I should have said "nobody writes code using `==` that depends on that logical equivalence." The `typeof x == "object" && !x => x === null` invariant I can certainly see being used in the wild, mainly to avoid the special-caseness of `null` being an object-according-to-`typeof`, but I can't for the life of me think of how to use the `typeof`/`==`/`===` relation. > It's not an equality, rather a two-way implication. It helps us reason about > all three of typeof, ==, and === as we evolve JS. It's not noise, and not > nothing. My perspective is that reasoning about `==`, and even to some extent `typeof`, is not that important, since they are both "broken." And thus such a connection does feel somewhat like noise; there are plenty of invariants you can state by just stringing together logical consequences of the language, but determining which of those are important is the trick. Anyway, I get it that good invariants are useful and that you at least find this particular invariant to be a good one, so we can leave it at that. I'd still love to see some plausible-in-the-wild code that could break if we lost this invariant, though. _______________________________________________ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
