typescript type array of arrays code example

Example 1: create array of... in typescript

let fruits: Array<string>;
fruits = ['Apple', 'Orange', 'Banana']; 

let ids: Array<number>;
ids = [23, 34, 100, 124, 44];

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

Example 3: array in typescript

const count = [...Array(5)];
count.map((_) => console.log('hi'));