```ts
export function digitCount(value: number): number {
  if (value === null || value === undefined) {
    throw new Error("Input cannot be null or undefined");
  }

  const isNegative = value < 0;
  const absValue = Math.abs(value);

  let count = 1;

  while (absValue > 9) {
    absValue /= 10;
    count++;
  }

  return isNegative ? count - 1 : count;
}
```