typescript-expert

To validate untrusted data boundaries in a TypeScript API, use Zod schemas to parse external inputs from unknown into typed data, enforcing runtime checks rather than relying solely on compile-time type safety.

The best way to prevent prototype pollution and XSS in TypeScript is to enforce strict tsconfig practices, ban unsafe patterns like `any` and unchecked type assertions, and apply security-focused dependency hygiene rules.

To model complex application state using discriminated unions in TypeScript, apply advanced type techniques like branded types, generics, and utility types to create safer interfaces and clearer error state modeling across your APIs.

TypeScript does not provide runtime type safety for external API inputs, which can lead to security vulnerabilities and crashes; you must implement runtime validation with Zod schemas to secure untrusted data boundaries.

You should avoid `any` and unchecked type assertions in strict TypeScript projects because they bypass compiler checks, creating security risks like injection and prototype pollution when handling external or untrusted data.

To test type contracts and error cases in a TypeScript module, use runtime tests alongside type-level checks like `expect-type` to ensure both behavior and type contracts remain correct and secure.