On 14 June 2012 18:10, Brendan Eich <[email protected]> wrote: > I agree on reflection with Wes and others who've objected that A ?: B has > the simplest interpretation as A ? A : B and therefore should not be used > for anything like (A !== undefined) ? A : B or (A != null) ? A : B. I noted > this as an open issue but I'm almost ready to flip the strawman back to ?? > and ??=. Comments on syntax? >
Do people see sufficient value in a second ternary operator that uses the same semantics for what's a non-value? E.g.: a = b ?? c : d; meaning a = b !== undefined ? c : d; If people *don't* see sufficient value in the second ternary (and the use cases are pretty limited), ?? and ??= are great. Ship 'em. If people *do* see sufficient value there, ?? is probably better suited to that than then the infix operator we're talking about, and the infix version will want a new name. ??: perhaps, which is easy to type and harkens to the second ternary. That would give us: a = b ?? c : d; a ??= b; a = b ??: c; I quite like the full set, but if it's just me, that's a non-argument. On semantics: CoffeeScript's use of != null to equate null and undefined > matches some users' habits, and helps to conceal the awkward fact of two > bottom-types in JS (@jashkenas just averred that was the goal). But such > concealment can never be perfect and other users will either want to > distinguish, or (what is more worrisome) will accidentally distinguish > (e.g. with !==) null from undefined. > FWIW: I never use null to mean "default me" in JS, and have never seen anyone do so. That's just my anecdotal experience. A couple of people have posted that they do, which is their anecdotal experience. I would rather the new operators just considered undefined as the non-value, not both undefined and null. But it wouldn't impact my code if it did (because I never use null in this way). It's just a preference. -- T.J.
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