safeParseInt

export function safeParseInt(
  value: string | undefined,
  defaultValue?: undefined,
): number | undefined;
export function safeParseInt(
  value: string | undefined,
  defaultValue: number,
): number;
export function safeParseInt(
  value: string | undefined,
  defaultValue: number | undefined = undefined,
) {
  if (typeof value === "undefined") return defaultValue;

  const parsed = Number.parseInt(value);
  if (Number.isNaN(parsed)) {
    return defaultValue;
  }
  return parsed;
}

Why

JavaScript includes Number.parseInt (recommended over parseInt) to convert string of an integer to a number. However, if we passed an invalid value, we will get NaN instead of undefined.

Number.parseInt("hi"); // NaN

Generally, we wouldn’t want that. On top of that, the safeParseInt function adds support for a fallback value. And it’s type-safe.