AssertHasProperty

Since 1.3.0

Ensure an object type has a specific property.

Signature

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

Parameters

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

Examples

Basic Usage

import type { AssertHasProperty } from 'uni-types'

type User = { name: string; age: number }
type HasName = AssertHasProperty<User, 'name'> // User
type NoEmail = AssertHasProperty<User, 'email'> // never

With Generic Types

type EnsureId<T> = AssertHasProperty<T, 'id'>
type Valid = EnsureId<{ id: number; name: string }> // { id: number; name: string }
type Invalid = EnsureId<{ name: string }> // never

With Symbol Properties

const key = Symbol('key')
type Obj = { [key]: string }
type Result = AssertHasProperty<Obj, typeof key> // Obj

Related

• AssertKeyof - Assert key exists on type
• RequireKeys - Make specific keys required