---
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>
