mapKeys

Creates a new object with the same values as obj, but with each key replaced by String(iteratee(value, key, obj)). Only own enumerable string keys are visited. Prototype-pollution keys (__proto__, constructor, prototype) returned by the iteratee are silently skipped. When two keys collide, the last write wins.

Try it

Import

import { mapKeys } from "1o1-utils";

import { mapKeys } from "1o1-utils/map-keys";

Signature

function mapKeys<T extends Record<string, unknown>>({
  obj,
  iteratee,
}: MapKeysParams<T>): Record<string, T[keyof T]>

Parameters

Name	Type	Required	Description
obj	Record<string, unknown>	Yes	The source object
iteratee	(value, key, obj) => string | number | symbol	Yes	Function returning the new key for each pair

Returns

Record<string, T[keyof T]> — A new object with transformed keys (input is not mutated).

Examples

mapKeys({
  obj: { a: 1, b: 2 },
  iteratee: (_value, key) => key.toUpperCase(),
});
// => { A: 1, B: 2 }

mapKeys({
  obj: { firstName: "Ana", lastName: "Silva" },
  iteratee: (_value, key) => key.replace(/[A-Z]/g, (c) => `_${c.toLowerCase()}`),
});
// => { first_name: "Ana", last_name: "Silva" }

Edge Cases

• Throws if obj is not a plain object.
• Throws if iteratee is not a function.
• Iteratee return value is coerced via String(...).
• Key collisions resolve last-write-wins.
• Prototype-pollution keys (__proto__, constructor, prototype) are skipped.
• Inherited properties are ignored — only own enumerable keys are visited.

Also known as

map keys, transform keys, rename keys, key mapper

Prompt suggestion

I'm using 1o1-utils (npm: https://www.npmjs.com/package/1o1-utils, GitHub: https://github.com/pedrotroccoli/1o1-utils, LLM context: https://pedrotroccoli.github.io/1o1-utils/llms.txt). Show me how to use mapKeys to convert a camelCase object's keys to snake_case