ObjectKeys

Creates a union of the keys of an object as they are returned by Object.keys. Unlike keyof, numeric keys are converted to strings and symbol keys are excluded, matching the runtime behavior of JavaScript, where object keys are always strings.

type Keys = ObjectKeys<T>;

Usage

ObjectKeys<T>

Use it when you want key types that match what Object.keys, Object.entries, or a for...in loop actually produce at runtime. It's especially handy for typing the result of Object.keys, which TypeScript widens to string[] by default.

import type { ObjectKeys } from 'es-toolkit/types';

// keyof keeps numeric keys as numbers, ObjectKeys converts them to strings.
type Keys = ObjectKeys<{ a: number; 1: string }>; // 'a' | '1'
type KeyofKeys = keyof { a: number; 1: string }; // 'a' | 1

// Type the result of Object.keys.
const obj = { a: 1, b: 2 };
const keys = Object.keys(obj) as Array<ObjectKeys<typeof obj>>; // Array<'a' | 'b'>

// Index signatures resolve to their string forms.
type StringKeys = ObjectKeys<Record<string, number>>; // string
type NumberKeys = ObjectKeys<Record<number, string>>; // `${number}`

// Symbol keys are excluded, like Object.keys does at runtime.
declare const sym: unique symbol;
type NoSymbols = ObjectKeys<{ a: number; [sym]: string }>; // 'a'

Type Parameters

• T: The object type to read keys from.