AssertKeyof

Since 1.3.0

Assert that K is a key of T at compile time.

Signature

type AssertKeyof<T, K> = K extends keyof T ? K : never

Parameters

Parameter	Description
T	The object type to check against
K	The key to verify

Examples

Basic Usage

import type { AssertKeyof } from 'uni-types'

type Result = AssertKeyof<{ name: string; age: number }, 'name'> // 'name'
type Failed = AssertKeyof<{ name: string }, 'email'> // never

With Union Keys

type Keys = 'name' | 'age'
type Result = AssertKeyof<{ name: string; age: number }, Keys> // 'name' | 'age'

With Symbol Keys

const sym = Symbol('id')
type Obj = { [sym]: number }
type Result = AssertKeyof<Obj, typeof sym> // typeof sym

Related

• AssertExtends - Assert type extends another
• AssertHasProperty - Ensure object has specific property