```ts
/** A code padded with zeros to a fixed width. */
export function padCode(code: string, width: number): string {
  if (typeof code !== "string" || typeof width !== "number") {
    throw new Error("Both code and width must be provided.");
  }

  let padded = code;
  while (padded.length < width) {
    padded = "0" + padded;
  }
  return padded;
}
```