typescript

name	typescript
description	TypeScript code style and optimization guidelines. Use when writing TypeScript code (.ts, .tsx, .mts files), reviewing code quality, or implementing type-safe patterns. Triggers on TypeScript development, type safety questions, or code style discussions.

TypeScript Code Style Guide

Types and Type Safety

• Avoid explicit type annotations when TypeScript can infer
• Avoid implicitly any; explicitly type when necessary
• Use accurate types: prefer Record<PropertyKey, unknown> over object or any
• Prefer interface for object shapes (e.g., React props); use type for unions/intersections
• Prefer as const satisfies XyzInterface over plain as const
• Prefer @ts-expect-error over @ts-ignore over as any
• Avoid meaningless null/undefined parameters; design strict function contracts

Async Patterns

• Prefer async/await over callbacks or .then() chains
• Prefer async APIs over sync ones (avoid *Sync)
• Use promise-based variants: import { readFile } from 'fs/promises'
• Use Promise.all, Promise.race for concurrent operations where safe

Code Structure

• Prefer object destructuring
• Use consistent, descriptive naming; avoid obscure abbreviations
• Replace magic numbers/strings with well-named constants
• Defer formatting to tooling

Performance

• Prefer for…of loops over index-based for loops
• Reuse existing utils in packages/utils or installed npm packages
• Query only required columns from database

Time Consistency

• Assign Date.now() to a constant once and reuse for consistency

Logging

• Never log user private information (API keys, etc.)
• Don't use import { log } from 'debug' directly (logs to console)
• Use console.error in catch blocks instead of debug package

Code Quality

• No any types unless absolutely necessary
• Check node_modules for external API type definitions instead of guessing
• NEVER use inline imports - no await import("./foo.js"), no import("pkg").Type in type positions, no dynamic imports for types. Always use standard top-level imports.
• NEVER remove or downgrade code to fix type errors from outdated dependencies; upgrade the dependency instead
• Always ask before removing functionality or code that appears to be intentional
• Never hardcode key checks with, eg. matchesKey(keyData, "ctrl+x"). All keybindings must be configurable. Add default to matching object (DEFAULT_EDITOR_KEYBINDINGS or DEFAULT_APP_KEYBINDINGS)