TypeScript template string literal type casing

CamelCase.ts

type DefaultSeparator = '_' | '-';

type CamelCase<S extends string, Separator extends string = DefaultSeparator, Beginning extends boolean = true>
  = S extends `${infer Character}${infer Rest}`
  ? Character extends Separator
    ? `${CamelCase<Capitalize<Rest>, Separator, Beginning>}`
    : `${Beginning extends true ? Lowercase<Character> : Character}${CamelCase<Rest, Separator, false>}`
  : '';

// Example: type T = "awaBbbCcc"
type T =
  | CamelCase<'Awa_bbb-ccc'>
  | CamelCase<'_Awa_bbb-ccc'>
  | CamelCase<'-Awa_bbb-ccc'>
;

This might be a bit computationally expensive 😅 so use at your own discretion 😄

Strings longer than 15 will trigger an error:

Type instantiation is excessively deep and possibly infinite.ts(2589)