Extract array item with conditional types

extract-array-item.ts

// with infer keyword
type ArrayItemInfer<T> = T extends Array<infer I> ? I : never;

// or just with regular index type 🙃
type ArrayItemRegular<T extends Array<any>> = T[number];


type People = { firstName: string; lastName: string; }[];

type PersonInfer = ArrayItemInfer<People>; // { firstName: string; lastName: string; } ✅
type PersonRegular = ArrayItemRegular<People>; // { firstName: string; lastName: string; } ✅