Here is how you can implement chunk function in TypeScript:

```ts
export function chunk<T>(items: readonly T[], size: number): T[][] {
  if (size <= 0 || Number.isNaN(size) || Math.floor(size) !== size) {
    throw new Error('Size must be a positive integer');
  }
  const result = [];
  for (let i = 0; i < items.length; i += size) {
    result.push(items.slice(i, i + size));
  }
  return result;
}
```