最後に`!`をつけると[[Nullish (JavaScript)|Nullish]]であることを示す[[TypeScript]]の構文。 ```ts declare const numberOrUndefined: number | undefined; declare const numberOrNull: number | null; declare const numberOrNullish: number | undefined | null; const a = numberOrUndefined!; // a: number const b = numberOrNull!; // b: number const c = numberOrNullish!; // c: number ``` <button class="playground"><a href="https://www.typescriptlang.org/play?#code/CYUwxgNghgTiAEYD2A7AzgF3igrgWwCMQYB5GAVRVADMBLFEYALm3yJngB94cqQ6GwANwAoUJFgJk6LLkLEyAORwQILOey6tVo8dDiJUmVvNIxlq2mgAW6tsS28a9Rltw6RI6cajwAvCbsZJTOggCEogD0kfCxAHoA-F5GWAT+gQrmKhARItGx8InJMojpGpkWEFbWufnxSUA">Playground</a></button>