01383-hard-camelize.ts

// ============= Test Cases =============
import type { Equal, Expect } from "./test-utils";

type cases = [
  Expect<
    Equal<
      Camelize<{
        some_prop: string;
        prop: { another_prop: string };
        array: [
          { snake_case: string },
          { another_element: { yet_another_prop: string } },
          { yet_another_element: string }
        ];
      }>,
      {
        someProp: string;
        prop: { anotherProp: string };
        array: [
          { snakeCase: string },
          { anotherElement: { yetAnotherProp: string } },
          { yetAnotherElement: string }
        ];
      }
    >
  >
];

// ============= Your Code Here =============

type Camelize<T extends Record<string, unknown>> = {
  [Key in keyof T as CamelizeKey<Key>]: T[Key] extends Record<string, unknown>
    ? Camelize<T[Key]>
    : T[Key] extends unknown[]
    ? CamelizeArr<T[Key]>
    : T[Key];
};

type CamelizeKey<T extends string | number | symbol> =
  T extends `${infer First}_${infer Rest}`
    ? CamelizeKey<`${First}${Capitalize<Rest>}`>
    : T;

type CamelizeArr<T extends unknown[]> = T extends [
  infer First extends Record<string, unknown>,
  ...infer Rest extends Record<string, unknown>[]
]
  ? [Camelize<First>, ...CamelizeArr<Rest>]
  : T;

type CamelizeObjAttrs<T extends Record<string, unknown>> = {
  [Key in keyof T as CamelizeKey<Key>]: T[Key];
};

type test1 = CamelizeKey<"some_prop">;
type test2 = CamelizeKey<"some">;
type test3 = CamelizeKey<"some_">;

type test4 = CamelizeObjAttrs<{
  some_prop: string;
  some_other_prop: number;
}>;

type test5 = Camelize<{
  some_prop: string;
  prop: { another_prop: string };
  array: [
    { snake_case: string },
    { another_element: { yet_another_prop: string } },
    { yet_another_element: string }
  ];
}>;
const Test5: test5 = {
  someProp: "hi",
  prop: { anotherProp: "hi" },
  array: [
    { snakeCase: "hi" },
    { anotherElement: { yetAnotherProp: "hi" } },
    { yetAnotherElement: "hi" },
  ],
};

type test6 = CamelizeArr<
  [
    { snake_case: "hi" },
    { another_element: { yet_another_prop: "hi" } },
    { yet_another_element: "hi" }
  ]
>;
const Test6: test6 = [
  { snakeCase: "hi" },
  { anotherElement: { yetAnotherProp: "hi" } },
  { yetAnotherElement: "hi" },
];