function toUserDomain toUserDomain(userDomain: string): UserDomain Check hostname subdomain against UserDomain. Examples ▶Valid user domain import { toUserDomain } from './user_utils.ts' const userDomain = toUserDomain('john-doe') console.assert(userDomain === 'john-doe') ▶Invalid user domain import { toUserDomain } from './user_utils.ts' try { const userDomain = toUserDomain('johndont') } catch (error) { console.assert(error instanceof Error) } Parameters userDomain: string Hostname to assert. Return Type UserDomain Asserted user domain.