TypeScript

import { nanoid } from 'nanoid'
 
const id: string = nanoid()
const shortId: string = nanoid(10)

import { nanoid } from 'nanoid'
 
declare const userIdBrand: unique symbol
type UserId = string & { [userIdBrand]: true }
 
declare const postIdBrand: unique symbol
type PostId = string & { [postIdBrand]: true }
 
interface User {
  id: UserId
  name: string
}
 
interface Post {
  id: PostId
  authorId: UserId
  title: string
}
 
// Generate typed IDs
const user: User = {
  id: nanoid<UserId>(),
  name: 'Alice'
}
 
const post: Post = {
  id: nanoid<PostId>(),
  authorId: user.id, // ✅ Type-safe
  title: 'Hello World'
}
 
// ❌ Type error: Can't assign PostId to UserId
// const wrongPost: Post = {
//   id: nanoid<PostId>(),
//   authorId: nanoid<PostId>(), // Error!
//   title: 'Hello'
// }

import { customAlphabet } from 'nanoid'
 
type HexId = string & { __brand: 'HexId' }
 
const hexNanoid = customAlphabet<HexId>('0123456789abcdef', 16)
 
const id: HexId = hexNanoid()

function nanoid<Type extends string = string>(
  size?: number
): Type

function customAlphabet<Type extends string = string>(
  alphabet: string,
  defaultSize?: number
): (size?: number) => Type

function customRandom<Type extends string = string>(
  alphabet: string,
  size: number,
  random: (bytes: number) => Uint8Array
): (size?: number) => Type