Here is the updated version of solution.ts that uses array methods to achieve the same result:
```typescript
export interface User {
  email: string;
  active: boolean;
}

/** The lowercased addresses of the active users, in order. */
export function activeEmails(users: readonly User[]): string[] {
   return users.filter(user => user.active)
               .map(user => user.email.toLowerCase());
}
```