Rules: typescript

TypeScript Rules

Affected files

These rules apply to files matching the following patterns:

• **/*.ts
• **/*.tsx
• **/*.mts

Detailed rules

TypeScript Rules

Strict Mode

• IMPORTANT: Strict mode enabled ("strict": true)
• Do not disable TypeScript checks
• Fix type errors, do not ignore them

Type Safety

• IMPORTANT: No any except documented exceptional cases
• YOU MUST define interfaces for complex objects
• Prefer unknown over any when the type is unknown
• Use type guards for narrowing

Types vs Interfaces

• Prefer type for unions and intersections
• Prefer interface for extensible objects
• Use interface for public APIs

Naming Conventions

Type	Convention	Example
Variables/Functions	camelCase	getUserById
Classes/Interfaces	PascalCase	UserService
Constants	SCREAMING_SNAKE	MAX_RETRY_COUNT
Generic types	T, K, V or descriptive	TData, TError
Enums	PascalCase (name and values)	UserRole.Admin

File Naming

Type	Convention	Example
React components	PascalCase	UserCard.tsx
Services/Utils	kebab-case	user-service.ts
Types/Interfaces	kebab-case or PascalCase	user-types.ts
Tests	same name + .test	user-service.test.ts

Best Practices

• Pure functions when possible
• Data immutability
• Single Responsibility Principle
• DRY but not at the expense of readability
• Avoid side effects in functions

Automatic application

These rules are automatically applied by Claude during:

• Reading the matching files
• Modifying code
• Suggestions and fixes

---

See also

• Back to rules
• Architecture