```ts
export function fieldOf(record: Record<string, number>, field: string): number {
  if (!record.hasOwnProperty(field)) {
    throw new Error(`Record '${JSON.stringify(record)}' does not have field '${field}'`);
  }
  return record[field];
}

export function sortPairs(records: Record<string, number>[], field: string): Record<string, number>[] {
  return records.sort((a, b) => {
    const va = a[field];
    const vb = b[field];
    if (va === vb) {
      return 0;
    }
    return va < vb ? -1 : 1;
  });
}
```