TypeScript Development (5.x)

Core Philosophy

1. Strict Mode Always

   • Enable all strict checks in tsconfig
   • Treat any as a bug—use unknown for untrusted input
   • noUncheckedIndexedAccess, exactOptionalPropertyTypes

2. Interface vs Type

   • interface for object shapes (extensible, mergeable)
   • type for unions, intersections, mapped types
   • interface for React props and public APIs

3. Discriminated Unions

   • Literal kind/type tag for variants
   • Exhaustive switch with never check
   • Model states as unions, not boolean flags