TypeScript Patterns We Use in Every Full-Stack Project

TypeScript isn't just about adding types to JavaScript. Used well, it becomes a design tool that shapes your architecture and catches errors before they reach production.

Branded Types for Domain Safety

We use branded types to prevent accidental misuse of primitive values:

A UserId and an OrderId are both strings, but they represent fundamentally different concepts. Branded types make it impossible to pass one where the other is expected.

Discriminated Unions for State Machines

UI state often maps to a finite set of states. Instead of boolean flags, we model state as discriminated unions. This eliminates impossible states like having both isLoading and isError be true simultaneously.

Zod for Runtime Validation

TypeScript types disappear at runtime. For API boundaries, form inputs, and external data, we use Zod schemas that provide both compile-time types and runtime validation in one definition.

Utility Types We Use Daily

• Pick and Omit: Create precise types for API responses without exposing internal fields
• Record: Type-safe dictionaries for lookup tables and configurations
• Extract and Exclude: Filter union types for specific handlers

API Contract Patterns

For full-stack Next.js apps, we define API contracts as shared types:

• Request schemas validated with Zod on the server
• Response types inferred from the schema
• Client-side hooks that are fully typed end-to-end

Error Handling

We use a Result type pattern instead of throwing exceptions. Every function that can fail returns either a success value or a typed error. This forces callers to handle errors explicitly and makes error paths visible in the type system.

Conclusion

These patterns add minimal overhead but dramatically reduce bugs and improve team velocity. TypeScript's type system is powerful enough to encode most business rules — use it.