typed-object-keys

A tiny typed wrapper around Object.keys for TypeScript.

Object.keys returns string[], which means TypeScript loses the relationship between an object and its known keys. typed-object-keys keeps that relationship at the type level while preserving the exact same runtime behavior as Object.keys.

Installation

npm install typed-object-keys

pnpm add typed-object-keys

yarn add typed-object-keys

bun add typed-object-keys

Usage

import objectKeys from "typed-object-keys";

const user = {
  id: "user_123",
  name: "Ada Lovelace",
  active: true,
};

const keys = objectKeys(user);
//    ^? Array<"id" | "name" | "active">

for (const key of keys) {
  const value = user[key];
  // key is typed as "id" | "name" | "active"
  // value is typed as string | boolean
}

API

objectKeys(object)

function objectKeys<TObject extends object>(object: TObject): Array<keyof TObject>;

Returns the enumerable own property names of object, typed as keys of the provided object type.

This package is intentionally a zero-dependency wrapper around Object.keys. It does not change JavaScript runtime behavior:

• only enumerable own properties are returned
• symbol keys are not returned
• numeric keys follow Object.keys and are returned as strings at runtime
• key order is the same as Object.keys

Why

This removes the common local cast:

const keys = Object.keys(user) as Array<keyof typeof user>;

and replaces it with:

const keys = objectKeys(user);

Package

• ESM only
• TypeScript declarations included
• No runtime dependencies
• Tree-shakeable

Development

Install dependencies:

vp install

Run validation:

vp check
vp test

Build the package:

vp pack

License

MIT