typescript:functional-patterns

Use discriminated unions and Algebraic Data Types (ADTs) to model exhaustive state machines in TypeScript. Apply an exhaustive switch statement with an assertNever utility to enforce compile-time guarantees across all possible states.

The best way to handle nullable values and errors in TypeScript domain logic is using Option and Result types. These utilities provide explicit error handling, forcing callers to safely resolve operations without relying on exceptions or null checks.

Enforce domain invariants like validated IDs and units at compile time by using branded types in TypeScript. This pattern tags primitive values with structural markers, ensuring only validated data passes through your domain models.

Yes, you can use discriminated unions for safe data parsing and configuration migrations. They enable strict pattern matching and compile-time exhaustiveness checks, preventing unhandled states during data transformations and safe migrations.

You should avoid Result types when migrating existing codebases that heavily rely on try-catch exception handling, as mixing both patterns can complicate logic. Result types work best for predictable, recoverable domain errors rather than unexpected runtime failures.