# Typescript Language

> Apply modern TypeScript standards for type safety and maintainability. Use when working with types, interfaces, generics, enums, unions, or tsconfig settings.

- **Type:** Skill
- **Install:** `agentstack add skill-hoangnguyen0403-agent-skills-standard-typescript-language`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [HoangNguyen0403](https://agentstack.voostack.com/s/hoangnguyen0403)
- **Installs:** 0
- **Category:** [Agent Skills](https://agentstack.voostack.com/c/agent-skills)
- **Latest version:** 0.1.0
- **License:** Apache-2.0
- **Upstream author:** [HoangNguyen0403](https://github.com/HoangNguyen0403)
- **Source:** https://github.com/HoangNguyen0403/agent-skills-standard/tree/develop/.agents/skills/typescript/typescript-language
- **Website:** https://www.npmjs.com/package/agent-skills-standard

## Install

```sh
agentstack add skill-hoangnguyen0403-agent-skills-standard-typescript-language
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# 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}`.
- **Discriminated Unions**: Literal kind property to narrow 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 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` or `as unknown as T`.
- **Checklist**: Check method existence, match error constants, satisfy required properties.
- **References**: See [references/TESTING.md](references/TESTING.md) for common issues/solutions.

## Code

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

// Satisfies (Validate + Infer)
const cfg = { port: 3000 } satisfies Record;

// Discriminated Union
type Result = { 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](references/REFERENCE.md).

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [HoangNguyen0403](https://github.com/HoangNguyen0403)
- **Source:** [HoangNguyen0403/agent-skills-standard](https://github.com/HoangNguyen0403/agent-skills-standard)
- **License:** Apache-2.0
- **Homepage:** https://www.npmjs.com/package/agent-skills-standard

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-hoangnguyen0403-agent-skills-standard-typescript-language
- Seller: https://agentstack.voostack.com/s/hoangnguyen0403
- Browse the marketplace: https://agentstack.voostack.com/browse

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Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.