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"

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.