Age Calculator with responsive UI made using grid

Hey Robert 👋, congratulations on solving this challenge

Your date validation is good, but if you want to calculate age in more concise and readable code you can look at my following code:

function calculateAge(day, month, year) {
  const today = new Date();
  const birthDate = new Date(year, month - 1, day);

  //Date Validation
  const isDayValid = birthDate.getDate() === day;
  const isMonthValid = birthDate.getMonth() === month - 1;
  const isYearValid = birthDate.getFullYear() === year;

  if (!isDayValid || !isMonthValid || !isYearValid) {
    isInputValid.value = false;
    return;
  }

  //calculating difference of current date and birthdate

  let ageYears = today.getFullYear() - birthDate.getFullYear();
  let ageMonths = today.getMonth() - birthDate.getMonth();
  let ageDays = today.getDate() - birthDate.getDate();

  if (ageMonths <= 0) {
    ageMonths += 12;
    ageYears--;
  }

  if (ageDays < 0) {
    const lastMonthDate = new Date(
      today.getFullYear(),
      today.getMonth(),
      0
    ).getDate();
    ageDays += lastMonthDate;
    ageMonths--;
  }


  //Age:
  console.log(ageYears, ageMonths, ageDays);
}

I hope this will help

Regards,

Shahjahan