Last of Array

Disclosure

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Problem Description

TypeScript 4.0 is recommended in this challenge

Implement a generic Last<T> that takes an Array T and returns its last element.

For example:

type arr1 = ['a', 'b', 'c']
type arr2 = [3, 2, 1]
 
type tail1 = Last<arr1> // expected to be 'c'
type tail2 = Last<arr2> // expected to be 1

Solutions

Approach 1: Using infer

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

Approach 2: Without infer

type Last<T extends any[]> = [any, ...T][T['length']];