# Typescript Best Practices

> Enforces TypeScript best practices and modern patterns Use when this capability is needed.

- Skill: `tomevault-io/typescript-best-practices-4` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/typescript-best-practices-4`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/typescript-best-practices-4/raw
- Safety review: pending
- 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-best-practices-4

---


# TypeScript Best Practices

## When to Use

Use this skill when:
- Writing new TypeScript code
- Reviewing TypeScript pull requests
- Refactoring JavaScript to TypeScript

## Triggers

Activated when editing `.ts` or `.tsx` files in the project.

## Rules

### Always
- Always use `const` for variables that won't be reassigned
- Always use explicit return types on exported functions
- Always prefer `interface` over `type` for object shapes

### Never
- Never use `any` — use `unknown` instead
- Never use `var` — use `const` or `let`
- Never ignore TypeScript errors with `@ts-ignore`

## Examples

```typescript
// Good: explicit return type
export function calculateTotal(items: Item[]): number {
  return items.reduce((sum, item) => sum + item.price, 0);
}
```

```typescript
// Good: discriminated union
type Result<T> =
  | { success: true; data: T }
  | { success: false; error: Error };
```

## Boundaries

- Do not modify `tsconfig.json` without explicit permission
- Do not add new dependencies without checking existing utilities
- Focus only on TypeScript patterns, not runtime behavior

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