```ts
function rowKey(name: string): string {
  return name.charAt(0).toUpperCase();
}

function indexRows(names: string[]): Record<string, string[]> {
  if (names.length === 0) return {};

  const result: Record<string, string[]> = {};
  names.forEach((name, index) => {
    const key = rowKey(name);
    if (!result[key]) result[key] = [];
    result[key].push(name);
  });

  return result;
}
```