Typescript best practices

---
description: Standards for TypeScript development.
globs:
alwaysApply: false
---

# TypeScript Best Practices
Standards for TypeScript development. Auto-included for TypeScript and TSX files.
<rule>
name: typescript_best_practices
description: TypeScript coding standards and type safety guidelines. Auto-included for TypeScript and TSX files.
globs: ["**/*.{ts,tsx}"]
filters:
- type: file_extension
pattern: "\.(ts|tsx)$"
actions:
- type: suggest
message: |
Follow these TypeScript best practices:
    1. Type Safety Configuration:
        - Enable strict mode in tsconfig.json
        - Use noImplicitAny for better type inference
        - Enable strictNullChecks for null safety
        - Implement strict property initialization
    2. Type Definitions:
        - Use interfaces for object shapes
        - Implement type aliases for unions/intersections
        - Define explicit return types for functions
        - Use generics for reusable type patterns
    3. Type Utilities:
        - Leverage built-in utility types (Partial, Pick, etc.)
        - Use type guards for runtime type checking
        - Implement mapped types for type transformations
        - Use conditional types when appropriate
    4. Type Organization:
        - Keep type definitions close to their usage
        - Create separate type declaration files when needed
        - Use namespaces sparingly
        - Prefer union types over enums
    5. Type Best Practices:
        - Avoid type assertions unless necessary
        - Use unknown instead of any when possible
        - Implement proper error types
        - Use readonly when appropriate
examples:
- input: |
// Bad: Implicit any
function process(data) {
return data.value;
}
- // Good: Explicit typing
interface Data {
value: string;
}
- function process(data: Data): string {
return data.value;
}
output: "Use explicit type definitions instead of implicit any"
- input: |
// Bad: Type assertion
const value = someValue as string;
- // Good: Type guard
function isString(value: unknown): value is string {
return typeof value === 'string';
}
- if (isString(someValue)) {
// value is typed as string here
}
output: "Use type guards instead of type assertions for runtime type checking"
metadata:
priority: high
version: 1.0
</rule>