sdlc-typescript-patterns

TypeScript discipline for any JavaScript/TypeScript project (frontend + backend): strict mode, type design, generics, narrowing, error types, module resolution, tsconfig hygiene. Apply when the project has tsconfig.json and typescript in devDependencies. Stack-agnostic — referenced by every JS/TS framework plugin in the marketplace. Use this skill to: - Write types that catch bugs at compile time, not runtime. - Use generics, conditional types, and discriminated unions correctly. - Avoid any, unknown, and unsafe casts. - Match the project's tsconfig strictness level. - Type third-party libraries (with @types/* or declaration files). Do NOT use this skill for: - Plain JavaScript projects (no tsconfig.json). - Framework-specific type idioms (React component props, Vue defineProps, Angular signals — those live in framework plugins' own conventions skills). - tRPC/Zod runtime-validation specifics — handled by validation libs at the boundary.