Check if given type is empty object | TypeScript Community | Page 1

warped swift Apr 7, 2023, 2:52 PM

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So, this is the example;

type ExampleType<T extends object> = Base & T === {} ? {} : { props: T }

Just like this, if T is not empty object, props is going to be defined, else we won't extends Base.

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When I do T extends {}, it does not work

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Check if given type is empty object

tight mica Apr 7, 2023, 3:20 PM

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@warped swift I'd be careful with this because {} doesn't really mean "empty object", it means an interface with no specified properties, but this seems to do essentially what you want?

final lionBOT Apr 7, 2023, 3:20 PM

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type HasNoKnownProperties<T> = {} extends T ? "Yes" : "No";

type Example1 = HasNoKnownProperties<{}>
//   ^? - type Example1 = "Yes"
type Example2 = HasNoKnownProperties<{ x: string }>
//   ^? - type Example2 = "No"

warped swift Apr 7, 2023, 7:52 PM

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ohh

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I was doing the opposite, T extends {} : "No", and it is always Yes

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amazing, I didn't know that

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Thank you so much @tight mica

#Check if given type is empty object