Brand Types

Create nominal types for type-safe branding.

Brand

Create a branded type that cannot be accidentally mixed with other types.

import type { Brand } from 'uni-types'

type UserId = Brand<string, 'UserId'>
type OrderId = Brand<string, 'OrderId'>

const userId: UserId = 'user-123' as UserId
const orderId: OrderId = 'order-456' as OrderId

// These won't mix - type safety!
// const wrong: OrderId = userId  // Error!

Use Cases

• IDs: Prevent mixing different entity IDs
• Validated Data: Mark data that has been validated
• Units: Distinguish different unit types

type ValidatedEmail = Brand<string, 'ValidatedEmail'>
type Celsius = Brand<number, 'Celsius'>
type Fahrenheit = Brand<number, 'Fahrenheit'>

Unbrand

Extract the underlying type from a branded type.

import type { Unbrand } from 'uni-types'

type UserId = Brand<string, 'UserId'>
type RawId = Unbrand<UserId>  // string

BrandedString & BrandedNumber

Convenience types for common branded patterns.

import type { BrandedString, BrandedNumber } from 'uni-types'

type Username = BrandedString<'Username'>
type Port = BrandedNumber<'Port'>