es-toolkit/dist/types/ToCamelCaseKeys.d.ts

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

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

//#region src/types/ToCamelCaseKeys.d.ts
type SnakeToCamel<S extends string> = S extends `${infer H}_${infer T}` ? `${Lowercase<H>}${Capitalize<SnakeToCamel<T>>}` : Lowercase<S>;
type PascalToCamel<S extends string> = S extends `${infer F}${infer R}` ? `${Lowercase<F>}${R}` : S;
/** If it's snake_case, apply the snake_case rule; for uppercase keys, lowercase the entire string; otherwise, just lowercase the first letter (including PascalCase → camelCase). */
type AnyToCamel<S extends string> = S extends `${string}_${string}` ? SnakeToCamel<S> : S extends Uppercase<S> ? Lowercase<S> : PascalToCamel<S>;
/**
 * Converts the keys of `T` to camelCase recursively.
 *
 * This is the return type of the `toCamelCaseKeys` 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 = { user_id: number; first_name: string };
 * type Converted = ToCamelCaseKeys<Response>;
 * // => { userId: number; firstName: string }
 */
type ToCamelCaseKeys<T> = T extends NonPlainObject ? T : T extends any[] ? Array<ToCamelCaseKeys<T[number]>> : T extends Record<string, any> ? { [K in keyof T as AnyToCamel<Extract<K, string>>]: ToCamelCaseKeys<T[K]> } : T;
//#endregion
export { ToCamelCaseKeys };