array in array in typescript code example

Example 1: typescript array

// let arr_name, elemType[];
let list: number[] = [1, 2, 3];
// Generic array type, Array<elemType>:
let list: Array<number> = [1, 2, 3];

Example 2: typescript one of array

function stringLiterals<T extends string>(...args: T[]): T[] { return args; }
type ElementType<T extends ReadonlyArray<unknown>> = T extends ReadonlyArray<infer ElementType> ? ElementType : never;

const values = stringLiterals('A', 'B');
type Foo = ElementType<typeof values>;

const v1: Foo = 'A' // This should work
const v2: Foo = 'D' // This should give me an error since 'D' doesn't exist in values