es-toolkit/dist/types/ToPascalCaseKeys.d.mts

A state-of-the-art, high-performance JavaScript utility library with a small bundle size and strong type annotations.

import { NonPlainObject } from "../_internal/NonPlainObject.mjs";

//#region src/types/ToPascalCaseKeys.d.ts
type SnakeToPascal<S extends string> = S extends `${infer H}_${infer T}` ? `${Capitalize<Lowercase<H>>}${Capitalize<SnakeToPascal<T>>}` : Capitalize<Lowercase<S>>;
type CamelToPascal<S extends string> = S extends `${infer F}${infer R}` ? `${Uppercase<F>}${R}` : S;
/** If it's snake_case, apply the snake_case rule; for uppercase keys, lowercase and capitalize the entire string; otherwise, just uppercase the first letter (including camelCase → PascalCase). */
type AnyToPascal<S extends string> = S extends `${string}_${string}` ? SnakeToPascal<S> : S extends Uppercase<S> ? Capitalize<Lowercase<S>> : CamelToPascal<S>;
/**
 * Converts the keys of `T` to PascalCase recursively.
 *
 * This is the return type of the `toPascalCaseKeys` function. Recurses into
 * plain objects and arrays; built-in objects like `Date`, `Map`, and functions
 * pass through unchanged.
 *
 * @template T - The type whose keys are converted.
 *
 * @example
 * type Response = { userId: number; firstName: string };
 * type Converted = ToPascalCaseKeys<Response>;
 * // => { UserId: number; FirstName: string }
 */
type ToPascalCaseKeys<T> = T extends NonPlainObject ? T : T extends any[] ? Array<ToPascalCaseKeys<T[number]>> : T extends Record<string, any> ? { [K in keyof T as AnyToPascal<Extract<K, string>>]: ToPascalCaseKeys<T[K]> } : T;
//#endregion
export { ToPascalCaseKeys };