Agent-Skills.md

Agent Skills: TypeScript Language Patterns

Modern TypeScript standards for type safety and maintainability. Use when working with types, interfaces, generics, enums, unions, or tsconfig settings. (triggers: **/*.ts, **/*.tsx, tsconfig.json, type, interface, generic, enum, union, intersection, readonly, const, namespace)

UncategorizedID: hoangnguyen0403/agent-skills-standard/typescript-language

Repository

hoangnguyen0403/agent-skills-standard
HoangNguyen0403License: Apache-2.0
362103

Install this agent skill to your local

pnpm dlx add-skill https://github.com/HoangNguyen0403/agent-skills-standard/tree/HEAD/.agent/skills/typescript/typescript-language

Skill Files

Browse the full folder contents for typescript-language.

Download Skill

Loading file tree…

.agent/skills/typescript/typescript-language/SKILL.md

Skill Metadata

Name
typescript-language
Description
'Modern TypeScript standards for type safety and maintainability. Use when working with types, interfaces, generics, enums, unions, or tsconfig settings. (triggers: **/*.ts, **/*.tsx, tsconfig.json, type, interface, generic, enum, union, intersection, readonly, const, namespace)'

TypeScript Language Patterns

Priority: P0 (CRITICAL)

Implementation Guidelines

  • Type Annotations: Explicit params/returns. Infer locals.
  • Interfaces vs Types: interface for APIs (supports declaration merging). type for unions, intersection types, mapped/conditional types.
  • Strict Mode: strict: true. Null Safety: ?. and ?? — Use narrowing instead. Avoid non-null assertion (!) operator.
  • Enums: Literal unions or as const. No runtime enum.
  • Generics: Reusable, type-safe code.
  • Type Guards: typeof, instanceof, predicates.
  • Utility Types: Partial, Pick, Omit, Record.
  • Immutability: readonly arrays/objects. Const Assertions: as const, satisfies.
  • Template Literals: on${Capitalize<string>}.
  • Discriminated Unions: Literal kind property to narrow the type safely. Switch on discriminant.
  • Advanced: Mapped, Conditional, Indexed types.
  • Access: Default public. Use private/protected or #private.
  • Branded Types: string & { __brand: 'Id' }.

Anti-Patterns

  • NEVER use any: Use unknown or a specific interface instead.
  • No Function: Use signature () => void.
  • No enum: Runtime cost.
  • No !: Avoid non-null assertion (!). Use narrowing (typeof, instanceof, if-checks).
  • No Lint Disable: Fix root cause; never suppress.

Testing

  • Mocking: Use jest.Mocked<T> or as unknown as T.
  • Checklist: Check method existence, match error constants, satisfy required properties.
  • References: See references/TESTING.md for common issues/solutions.

Code

// Branded Type
type UserId = string & { __brand: 'Id' };

// Satisfies (Validate + Infer)
const cfg = { port: 3000 } satisfies Record<string, number>;

// Discriminated Union
type Result<T> = { kind: 'ok'; data: T } | { kind: 'err'; error: Error };

Verification

After any type change that crosses module boundaries or involves generics, unions, conditional types, or branded types: call getDiagnostics (typescript-lsp MCP tool) to confirm no type errors before finalizing.

References

For advanced type patterns and utility types: See references/REFERENCE.md.