Validate `unknown` in TypeScript Without a Schema Library

Описание и применение

Как безопасно преобразовать значение unknown из ненадёжных источников в тип, используя is-kit‑гварды, без полной схемы валидации.

Задача

How to safely convert an unknown value from untrusted boundaries into a usable type without relying on a full schema library?

Результат

Using is-kit guards provides a lightweight, composable way to validate unknown values, giving both runtime safety and TypeScript narrowing without the overhead of a full schema library.

Рабочий процесс

• Declare input: unknown from an untrusted source.
• Import is-kit predicates (isString, oneOfValues, struct, etc.).
• Define a guard, e.g., const isUser = struct({id: isString, name: isString, role: oneOfValues("admin","member")});
• Use the guard: if (isUser(input)) { /* input is now narrowed */ }
• Optionally use safeParse(isUser, input) to get a {valid, value} result for control flow.
• Handle invalid cases by returning an error response or similar.
• Render or process the validated value.

Доказательства

as User changes what the compiler believes. It does not inspect the runtime value.

Источник

With is-kit, we can build a guard like this…

Источник

safeParse gives us a small tagged result…

Источник

safeJsonParse…

Источник