software-best-design-patterns-skill

2026-edition design-patterns reference for TypeScript 6. Covers all 23 Gang-of-Four patterns, PoEAA enterprise patterns (Repository, Unit of Work, Service Layer, DTO, Identity Map, Lazy Load), modern TS idioms (Result, Discriminated Union State, Branded Types, Type-State, Dependency Injection, Hooks, Signals, Reducer, Middleware), resilience (Circuit Breaker, Retry+Backoff, Saga, Outbox, Idempotency), plus references on SOLID, anti-patterns, TS 6 features (strict-default, ES2025, Temporal, satisfies, const params, NoInfer, using), functional patterns, architectural styles (Hexagonal, Clean, CQRS, Event Sourcing, DDD), and testing. Use when designing architecture, refactoring code, or when code exhibits symptoms like growing switch statements, deep inheritance, tight coupling, dual-write inconsistencies, throwing for expected errors, stringly-typed IDs, unbounded retry loops, or boolean state flags.