Disclosure
Most of the problems under my TypeHero Challenges folder were either obtained from typehero.dev or from type-challenges repo. Purpose of these articles are just to document my approaches for my easy reference. Please visit the respective links for more info.
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Problem Description
Implement a generic First<T> that takes an Array T and returns its first element’s type.
For example:
type arr1 = ['a', 'b', 'c']
type arr2 = [3, 2, 1]
type head1 = First<arr1> // expected to be 'a'
type head2 = First<arr2> // expected to be 3Solutions
Approach 1: Using T["length"]
type First<T extends any[]> = T["length"] extends 0 ? never : T[0];Approach 2: Checking for empty array
type First<T extends any[]> = T extends [] ? never : T[0];Approach 3: Using infer
type First<T extends any[]> = T extends [infer First, ...any] ? First : never;