Refer: Medium - Pop

Describe

Implement a generic Pop<T> that takes an Array T and returns an Array without it’s last element. Include Extra.

For example

code snippetCopytypescript
type arr1 = ['a', 'b', 'c', 'd']
type arr2 = [3, 2, 1]

type re1 = Pop<arr1> // expected to be ['a', 'b', 'c']
type re2 = Pop<arr2> // expected to be [3, 2]

Extra: Similarly, can you implement Shift, Push and Unshift as well?

Test Cases

code snippetCopytypescript
import { Equal, Expect } from '@type-challenges/utils'

type cases = [Expect<Equal<Pop<[3, 2, 1]>, [3, 2]>>, Expect<Equal<Pop<['a', 'b', 'c', 'd']>, ['a', 'b', 'c']>>]

Solution

code snippetCopytypescript
// my solution (pop)
type Pop<T extends any[]> = T extends [...infer P, infer K] ? P : []

// my solution (shift)
type Pop<T extends any[]> = T extends [infer P, ...infer K] ? K : []

// my solution (unshift)
type Pop<T extends any[], U> = [U, ...T]

// my solution (push)
type Pop<T extends any[], U> = [...T, U]