typescript-best-practices

TypeScript patterns for type-first development, making illegal states unrepresentable, and exhaustive handling. Follows type-first, functional, and error handling patterns from CLAUDE.md. This skill covers language-specific idioms only. When working with React components ( .tsx , .jsx files or @react imports), always load react-best-practices alongside this skill. This skill covers TypeScript fundamentals; React-specific patterns (effects, hooks, refs, component design) are in the dedicated React skill. Use the type system to prevent invalid states at compile time. Discriminated unions for mutually exclusive states: Branded types for domain primitives: Const assertions for literal unions: Exhaustive switch with never check: For advanced type utilities beyond TypeScript builtins, consider type-fest : - Use discriminated unions, branded types, and const assertions to encode business rules in the type system and prevent invalid states at compile time - Validate at system boundaries with Zod schemas as single source of truth; infer TypeScript types automatically to keep types and validation in sync - Enforce exhaustive handling with never checks in switch statements and default cases; unhandled code paths become compile errors - Wrap external calls and async operations with contextual error messages; propagate failures rather than silently catching them - Load and validate...