function checks if date exists/ is date valid

dateExists.ts

function dateExists(year: number, month: number, day: number): boolean {
  if (typeof year !== "number") year = Number.parseInt(`${year}`, 10);
  if (typeof month !== "number") month = Number.parseInt(`${month}`, 10);
  if (typeof day !== "number") day = Number.parseInt(`${day}`, 10);
  if (year && month && day) {
    if (day >= 1 && day <= 31 && month >= 1 && month <= 12) {
      const d = `${day}`.padStart(2, "0");
      const m = `${month}`.padStart(2, "0");
      const y = `${year}`.padStart(4, "0");

      const datestring = `${y}-${m}-${d}`; // 2019-02-28
      const date = new Date(datestring).toJSON(); // 2019-02-28T00:00:00.000Z

      return date.startsWith(datestring);
    }
  }
  return false;
}

test.ts

import dateExists from "./dateExists.ts";

console.log(dateExists(2019, 2, 29)); // false
// 2019 is not a leap year, then February 29, 2019 is not valid