of options object. (#2) export function resolve( hostname: string, family?: "ipv4" | "ipv6", timeout?: number ): IPAddress[] {} 関数の必須引数は最大で 2つまで。オプション引数はオブジェクトとして渡す。 // GOOD. export interface ResolveOptions { family?: "ipv4" | "ipv6"; timeout?: number; } export function resolve( hostname: string, options: ResolveOptions = {} ): IPAddress[] {}