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Just shot myself in the foot today because #TypeScript enums start atPermalink On twitter.com
0, which is falsey. That means thatif (someEnumOrUndefined) {}won't work the way you expect. I'm wondering if:enum Foo { Bar = 1, Baz, }Should be a best practice? typescriptlang.org/play?target=7#code/KYOwrgtgBAYg9nKBvAUFdUBCBDATgGigHoioBeKABigCMBPKAE2ADNswAbAFzQxwC9CJclACMtBszaceAXxQoAxnBABnLrTwAuWAigAfKGBBSAliGCMR8OADocuANwpTLKAAoaeAJRRlauA5gWw44AHN3AHIvXChgAA9TdVVI70diUgAROGBVEEiNAAdccy5bBX91TX4dGwMjE1ZzS2sEe2x+Z1cPL35fSsDg0IjojrjE5NT04QAFEpAuVXKgA
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Mood +3 🙂
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This seems to have come up before in the @typescript repo but was dismissed because truthy/falsey behavior is occasionally useful and other languages have the same hazard. They suggest that thePermalink On twitter.com
0value should be the "Zero like" or "unspecified" value. github.com/microsoft/TypeScript/issues/7473
Mood +2 🙂
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@typescript I can agree with some of the specific points, but I don't see them as a compelling argument. Not every enum has a "Zero like" value and this is a very easy mistake to make with a complex "rethink the way you are designing enums" solution that most devs won't think of up front.Permalink On twitter.com
Mood +3 🙂
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I honestly feel that defaulting enums to 1 is a pretty clean solution here. Advanced usages which have a "Zero like" value or use it as a boolean can explicitly setPermalink On twitter.com
= 0, basic usages won't have this foot-gun.
Mood +7 🙂
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Migrating existing code would definitely be the toughest aspect. It's actually pretty mechanical since a schematic or codemod could just addOn twitter.com
= 1to all existing enums in a codebase, though #TypeScript doesn't really have that upgrade story, so I get the churn issue.
Mood +1 🙂
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The other solution would be to disallowPermalink On twitter.com
if (x as number) {}, since this is really an issue with 0 falsiness than anything with enums. I would personally be ok with that too, though I think people would likely push back on that even more strongly.
Mood +1 🙂