TypeScript Best Practices
1. Enable Strict Mode
Always use strict mode in tsconfig.json. It catches more errors at compile time:
- strict: true
- noImplicitAny: true
- strictNullChecks: true
2. Prefer Interfaces Over Types
Use interfaces for object shapes and types for unions, intersections, and primitives.
3. Avoid 'any' Like the Plague
Every 'any' is a type safety hole. Use unknown instead when the type is truly unknown, then narrow with type guards.
4. Use Discriminated Unions
For state management and API responses, discriminated unions provide exhaustive type checking.
5. Proper Error Handling
- Define custom error types
- Use Result/Either patterns for expected failures
- Let unexpected errors bubble up
- Type your error responses
6. Use Zod for Runtime Validation
TypeScript types disappear at runtime. Use Zod to validate external data (API responses, form inputs, environment variables).
7. Project Structure
- Group by feature, not by type
- Co-locate tests with source files
- Use barrel exports sparingly
- Keep types close to where they are used
8. Utility Types
Master built-in utility types: Partial, Required, Pick, Omit, Record, and ReturnType.
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