KebabCase

In this medium-level challenge, you'll replace the camelcase or pascalcase string with kebab-case.

type FooBarBaz = KebabCase<"FooBarBaz">
const foobarbaz: FooBarBaz = "foo-bar-baz"
 
type DoNothing = KebabCase<"do-nothing">
const doNothing: DoNothing = "do-nothing"

/* _____________ Your Code Here _____________ */

type KebabCase<S> = any

/* _____________ Test Cases _____________ */
import type { Equal, Expect } from '../helpers'

type cases = [
  Expect<Equal<KebabCase<'FooBarBaz'>, 'foo-bar-baz'>>,
  Expect<Equal<KebabCase<'fooBarBaz'>, 'foo-bar-baz'>>,
  Expect<Equal<KebabCase<'foo-bar'>, 'foo-bar'>>,
  Expect<Equal<KebabCase<'foo_bar'>, 'foo_bar'>>,
  Expect<Equal<KebabCase<'Foo-Bar'>, 'foo--bar'>>,
  Expect<Equal<KebabCase<'ABC'>, 'a-b-c'>>,
  Expect<Equal<KebabCase<'-'>, '-'>>,
  Expect<Equal<KebabCase<''>, ''>>,
  Expect<Equal<KebabCase<'😎'>, '😎

Detailed Explanation

type KebabCase<S extends string> = S extends `${infer Letter}${infer Rest}`
  ? Rest extends Uncapitalize<Rest>
    ? `${Uncapitalize<Letter>}${KebabCase<Rest>}`
    : `${Uncapitalize<Letter>}-${KebabCase<Rest>}`
  : S

How it works:

• First we constrain the type S to be a string.
• Then we use a template literal and infer to capture the first letter and the rest of the string.
• If the rest of the string is not capitalized, we return a a new string consisting of the first letter (but uncapitalized) and the rest of the string recursively passed into KebabCase<S2>.
• If the rest of the string is capitalized, we return a new string consisting of the first letter (but uncapitalized) and a hyphen (-) and the rest of the string recursively passed into KebabCase<S2>.

This challenge helps you understand TypeScript's advanced type system and how to apply this concept in real-world scenarios.