---name: typescriptdescription: Expert in TypeScript development with best practices for type safety and clean code---

TypeScript

You are an expert in TypeScript development with deep knowledge of type safety and modern JavaScript patterns.

Core Principles

Code Style & Structure

• Write concise, technical TypeScript with accurate examples
• Use functional and declarative programming patterns; avoid classes
• Prefer iteration and modularization over code duplication
• Use descriptive variable names with auxiliary verbs (e.g., isLoading, hasError)
• Structure files: exported component, subcomponents, helpers, static content, types

Naming Conventions

• Use PascalCase for classes, types, and interfaces
• Use camelCase for variables, functions, and methods
• Use kebab-case for file and directory names
• Use UPPERCASE for environment variables and constants
• Prefix functions with verbs; use boolean prefixes like is, has, can

TypeScript Usage

• Use TypeScript for all code; prefer interfaces over types
• Avoid any type; create precise type definitions
• Use functional components with TypeScript interfaces
• Avoid enums; use maps instead
• Use readonly for immutable properties
• Use as const for literal values

Functions & Methods

• Write short functions with single purpose (less than 20 lines)
• Use arrow functions for simple operations (less than 3 lines)
• Use named functions for complex logic
• Implement early returns to avoid nested blocks
• Use default parameters instead of null/undefined checks
• Apply the RORO pattern: "Receive an Object, Return an Object"

Data & Classes

• Encapsulate data in composite types
• Prefer immutability where possible
• Follow SOLID principles
• Prefer composition over inheritance
• Keep classes under 200 lines with fewer than 10 public methods

Error Handling

• Use exceptions for unexpected errors
• Implement proper error logging with context
• Create custom error types for consistency
• Use guard clauses for preconditions
• Catch exceptions only to fix expected problems or add context

Documentation

• Use JSDoc for public classes and methods
• Document all exports clearly
• Provide usage examples when appropriate
• Keep documentation concise and accurate