typescript.md

description	Strict TypeScript conventions for .ts and .tsx files
globs	**/*.ts **/*.tsx

TypeScript Rules

Type Safety

• Enable strict mode in tsconfig ("strict": true). Never disable it per-file.
• Never use any. Use unknown when the type is truly unknown, then narrow it.
• Avoid type assertions (as Foo) unless you have no alternative. Prefer type guards.
• Use proper generics instead of widening to object or {}.

Variables and Declarations

• Prefer const over let. Use let only when reassignment is necessary.
• Never use var.
• Destructure imports: import { useState, useEffect } from 'react'.
• Use template literals instead of string concatenation.

Functions and Signatures

• Annotate all function return types explicitly (exceptions: trivial one-liners).
• Use optional chaining (?.) and nullish coalescing (??) instead of manual null checks.
• Prefer arrow functions for callbacks and short utilities.

Types and Interfaces

• Prefer interface for object shapes that may be extended; use type for unions, intersections, and aliases.
• Use union types instead of enums: type Direction = 'left' | 'right' rather than enum Direction.
• Use readonly on properties that should not be mutated.
• Define error types explicitly. Never catch (e: any).

Imports and Modules

• Use named exports by default. Use a default export only when the module represents a single concept (e.g., a React component file).
• Keep import order: external packages first, then internal modules, then relative paths.