TypeScript Development Rules

Type Safety in Backend Implementation

Type Safety in Data Flow Input Layer (unknown) -> Type Guard -> Business Layer (Type Guaranteed) -> Output Layer (Serialization)

Backend-Specific Type Scenarios:

• API Communication: Always receive responses as unknown, validate with type guards
• Form Input: External input as unknown, type determined after validation
• Legacy Integration: Stepwise assertion like window as unknown as LegacyWindow
• Test Code: Always define types for mocks, utilize Partial<T> and vi.fn<[Args], Return>()

Coding Conventions