# Typescript

> Opinionated TypeScript code style and type safety rules. Activate when editing any `.ts` file — covers control flow, type safety, enums, and naming conventions. Use when this capability is needed.

- Skill: `tomevault-io/typescript-22` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/typescript-22`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/typescript-22/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/typescript-22

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# TypeScript Code Style

Strict, opinionated rules. Follow these to write correct code on the first draft.

## Control Flow

- **Early returns for guard clauses** — return early for error/edge cases to keep main logic flat
- **Always use block bodies** for `if` with `return` — never `if (!x) return;` on one line
- **Prefer positive conditions** — check what should happen, not what shouldn't. Does NOT apply to guard clauses, where negative checks are expected
- **No `else` after `return`** — if a branch returns, the next block needs no `else`
- **`switch` over chained `if`** — when checking the same variable against multiple values

## Type Safety

- **No `any`** — forbidden. Use `unknown` for uncertain types, generics to preserve/relate types
- **No non-null assertions (`!`)** — forbidden. Use optional chaining (`?.`) or guard clauses
- **Minimize `as` casting** — fix types at the source. Use generics, `satisfies`, or type guards instead
- **Generics over broad types** — prefer generic parameters over accepting broad types and casting results
- **Let TypeScript infer return types** — only annotate when needed (public APIs, recursion, or when inference produces the wrong type)

## Enums

**No enums** — forbidden. Use `as const` objects with derived types:

```typescript
const Status = {
  Active: 'active',
  Inactive: 'inactive',
} as const;

type Status = (typeof Status)[keyof typeof Status];
```

## Naming

- **Be descriptive** — prefer specificity over brevity. `activeUsers` not `data`, `sortByDate` not `process`
- **No `I`/`T` prefixes** — `User` not `IUser`, `Config` not `TConfig`

---
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<!-- tomevault:4.0:skill_md:2026-04-16 -->