ref-sp-js-typescriptlisted

# TypeScript ## Purpose Provide portable TypeScript defaults that keep types honest, runtime boundaries explicit, and code readable under strict settings. ## When to use this skill - Writing or refactoring TypeScript modules or scripts. - Deciding how to model states, responses, and shared types. - Reviewing TypeScript config and type-checking strictness. - Handling unknown external data safely. ## Scope Boundaries - Use this skill for strict TypeScript design, runtime boundaries, and package-level structure. - Use `ref-sp-js-react` when the main question is about React component structure, hooks, client-side state ownership, or React-specific dependency choices. - Use `ref-sp-js-next` when the main question is about Next.js framework structure, App Router, or Next-specific integrations. - Use `ref-sp-js-javascript` when the code intentionally stays in plain JavaScript with JSDoc rather than full TypeScript. - Use `ref-sp-dev-coding-patterns` for language-agnostic naming, comments, CLI ergonomics, and testing defaults. - Use `ref-sp-dev-projects-architecture` for generic feature-boundary or shared-utility decisions that are not TypeScript-specific. ## Defaults - Prefer strict mode and keep it strict. - Prefer `unknown` plus narrowing over `any`. - Prefer discriminated unions for stateful variants. - Prefer explicit runtime validation at trust boundaries. - Prefer inferred function return types by default when TypeScript can express the result cleanly from the implemen