TypeScript Best Practices in 2026

TypeScript has become essential for large-scale JavaScript projects. Here are the best practices for 2026.

Use Strict Mode

Always enable strict mode in your tsconfig.json:

{
  "compilerOptions": {
    "strict": true,
    "noUncheckedIndexedAccess": true
  }
}

Prefer Types Over Interfaces

Types are more flexible and provide better error messages:

type User = {
  id: string;
  name: string;
};

Use Discriminated Unions

For state management and complex types:

type LoadingState = 
  | { status: 'idle' }
  | { status: 'loading' }
  | { status: 'success'; data: User }
  | { status: 'error'; error: Error };

Leverage Utility Types

Built-in utility types save time:

type PartialUser = Partial<User>;
type ReadonlyUser = Readonly<User>;
type UserPreview = Pick<User, 'id' | 'name'>;

Avoid any

Use unknown instead when the type is truly unknown, then narrow it down.

Zod for Runtime Validation

Pair TypeScript with Zod for complete type safety including runtime validation.