```ts
/** The text, cut to limit characters with an ellipsis when it is longer. */
export function truncate(text: string, limit: number): string {
  /** Throw Error unless limit is an integer of at least 3. */
  if (typeof limit === "number" && isNaN(limit) || limit < 3) {
    throw new Error("Limit must be a positive integer");
  }
  if (text.length >= limit) {
    return text.slice(0, limit - 2) + "...";
  } else {
    return text;
  }
}
```