```ts
export function caseCount(text: string): number[] {
  const lowerCaseLetters = [...text].filter(char => char >= 'a' && char <= 'z');
  const upperCaseLetters = [...text].filter(char => char >= 'A' && char <= 'Z');

  return [upperCaseLetters.length, lowerCaseLetters.length];
}
```