Let me compound on that: Kotlin has a `!in` for "not in collection" and `!is` for "not an instance of". I've been using that language quite a bit lately out of necessity (better than Java, and all the other alternatives suck in some way), and those two operators just feel *wrong* to type. It's to the point I'm sometimes coding my way *out* of writing them. (No other feature uses this symbol except for literal logical negation.)
Oh, and as I mentioned before, `key in object` checks the prototype chain, which in my experience is not the thing you usually want to do. So I agree this is a Really Bad Idea™, for this above if not the Kotlin reference. On Wed, Jul 11, 2018, 11:24 Alex Vincent <ajvinc...@gmail.com> wrote: > ---------- Forwarded message ---------- >> From: Andrea Giammarchi <andrea.giammar...@gmail.com> >> To: Jordan Harband <ljh...@gmail.com> >> Cc: "es-discuss@mozilla.org" <es-discuss@mozilla.org> >> Bcc: >> Date: Wed, 11 Jul 2018 16:23:03 +0200 >> Subject: Re: Small Proposal "!in" >> and, as previously mentioned, `!obj.x` might have side effects through >> the accessor, as example in every lazily defined property that would be >> early defined (or anything else behind a getter that could do more than >> just telling the property is there and it's not truthy). >> > > Peanut gallery observation: I personally think !in is a Really Bad Idea, > or at least I'm not convinced that it's particularly useful. If it is > useful, then let one of the transpiling languages like CoffeeScript or > TypeScript demonstrate it first. > > Also, there's the little matter of pronunciation. I admit to a bit of > snarkiness when I first saw this proposal, but I didn't expect it to have > any traction. So I'll just say it: do we really want JavaScript to be a > "bangin' " language? > > Alex > > -- > "The first step in confirming there is a bug in someone else's work is > confirming there are no bugs in your own." > -- Alexander J. Vincent, June 30, 2001 > _______________________________________________ > es-discuss mailing list > es-discuss@mozilla.org > https://mail.mozilla.org/listinfo/es-discuss >
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