typescript-type/types/tuple.ts

Typescript type

/** Prepend */

export type Prepend<E, T extends any[]> = ((head: E, ...args: T) => any) extends ((...args: infer U) => any) ? U : T;

/** Head */

export type Head<T extends any[]> = T extends [any, ...any[]] ? T[0] : never;

/** Tail */

export type Tail<T extends any[]> = ((..._: T) => any) extends ((_: any, ...args: infer TT) => any) ? TT : never;

export type HasTail<T> = T extends ([] | [any]) ? false : true;

/** Last */

export type Last<T extends any[]> = {
  0: Last<Tail<T>>;
  1: Head<T>;
}[HasTail<T> extends true ? 0 : 1];

/** Length */

export type Length<T extends any[]> = T['length'];

export type SameLength<T1 extends any[], T2 extends any[]> = Length<T1> extends Length<T2> ? true : false;

export type TupleWithLength<N extends number, T2, I extends any[] = []> = {
  0: TupleWithLength<N, T2, Prepend<T2, I>>;
  1: I;
}[Length<I> extends N ? 1 : 0];

/** Drop */

export type Drop<N extends number, T extends any[], I extends any[] = []> = {
  0: Drop<N, Tail<T>, Prepend<any, I>>;
  1: T;
}[Length<I> extends N ? 1 : 0];