15 - Last of Array

[ashi009]

type Last<T extends any[]> = [any, ...T][T["length"]];

[vydimitrov]

Does not seem to be working or I am doing something worng here?

https://www.typescriptlang.org/play?#code/C4TwDgpgBAMghgZ2AHgCpQgD2BAdgEwSjlxAG0BdAPigF4oySQAaKAOg9QrNTICIANngDmwABZ8KFANwAoWQGMA9riRQARnABOALliIUSLQEtcwyjXoAWaUA

[mleg]

Great, very neat and clever!

[GreatAuk]

clever... What the fuck , Typescript

[Ahmed364051]

You are genius!!!😂

[paulopontovaz]

I ended up with the other solution, which uses infer. I have a question though: why can't we use T[T["length"]]? It gives me an error when I try it =/

[daolanfler]

I ended up with the other solution, which uses infer. I have a question though: why can't we use T[T["length"]]? It gives me an error when I try it =/

I guess it's because the length index overflows

[GideonMax]

I ended up with the other solution, which uses infer. I have a question though: why can't we use T[T["length"]]? It gives me an error when I try it =/

you need T[T.length-1], so the any is to shift the array once to the right

[GideonMax]

Does not seem to be working or I am doing something worng here?

https://www.typescriptlang.org/play?#code/C4TwDgpgBAMghgZ2AHgCpQgD2BAdgEwSjlxAG0BdAPigF4oySQAaKAOg9QrNTICIANngDmwABZ8KFANwAoWQGMA9riRQARnABOALliIUSLQEtcwyjXoAWaUA

that's because T["length"] is number since there is no predefined length, and since the first element of [any,...T] is any Last<string[]> is any

[EltonLobo07]

Does not seem to be working or I am doing something worng here?

https://www.typescriptlang.org/play?#code/C4TwDgpgBAMghgZ2AHgCpQgD2BAdgEwSjlxAG0BdAPigF4oySQAaKAOg9QrNTICIANngDmwABZ8KFANwAoWQGMA9riRQARnABOALliIUSLQEtcwyjXoAWaUA

type Last<T extends any[]> = [T extends (infer NT)[] ? NT : never, ...T][T["length"]]; should work.

[WanderedToLa]

Im inspired me thank you

[KNHui]

What about never:

type Last<T extends any[]> = [never, ...T][T["length"]];

[jericbas]

type Last<T extends unknown[]> = [unknown, ...T][T["length"]]

this is also working

[nomoreyou]

卧槽 牛逼

[huanganfree]

type Last<arr extends any[]> = arr extends [...leftProps: any[], infer L] ? L : never

this is also working

[jinyoung234]

type Last<T extends any[]> = T extends [...any, infer L] ? L : T

this is also working

[Qzhor]

type Last<T extends any[]> = T extends [...infer A, infer B] ? B : never

[Zum-Gluck]

卧槽 牛逼

nb

[dbfu]

type Last<T extends any[]> = T extends [infer F, ...infer R] ? R["length"] extends 0 ? F : Last<R> : never

[MarvinXu]

FYI, subtract operation on types is not natively supported. You can actually find type challenges for this: 2257・MinusOne 7561・Subtract

[im-jihoon]

wow...

[QingCT]

You are genius!!!

[keatkeat87]

Think Different

[TaR1z]

I'm so stupid

type Last<T extends Array<any>> = T extends [T[0]] ? T[0] : (
  T extends [T[0], ...infer U] ? Last<U> : never
);