CamelCase

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题目

实现 CamelCase<T> ，将 snake_case 类型的表示的字符串转换为 camelCase 的表示方式。

例如

type camelCase1 = CamelCase<"hello_world_with_types">; // 预期为 'helloWorldWithTypes'
type camelCase2 = CamelCase<"HELLO_WORLD_WITH_TYPES">; // 期望与前一个相同

解答

type IsAlphabet<T extends string> = Lowercase<T> extends Uppercase<T>
  ? false
  : true;

type CamelCase<
  S extends string,
  Result extends string = ""
> = S extends `${infer Left}${infer Rest}`
  ? IsAlphabet<Left> extends true
    ? Result extends `${infer Prefix}_`
      ? CamelCase<Rest, `${Prefix}${Uppercase<Left>}`>
      : CamelCase<Rest, `${Result}${Lowercase<Left>}`>
    : CamelCase<Rest, `${Result}${Left}`>
  : Result;