Calculate Age from Birthdate and set it into Age whenever the form loads or Birthdate changes

function calculateAge(executionContext) {
    var formContext = executionContext.getFormContext();
    var birthDateAttr = formContext.getAttribute("birthdate");   // Birthdate field logical name
    var ageAttr = formContext.getAttribute("new_age");           // Age field logical name

    if (!birthDateAttr || !ageAttr) return;

    var birthDate = birthDateAttr.getValue();
    if (!birthDate) {
        ageAttr.setValue(null);
        return;
    }

    var today = new Date();
    var age = today.getFullYear() - birthDate.getFullYear();

    // adjust if birthday hasn’t occurred yet this year
    if (
        today.getMonth() < birthDate.getMonth() ||
        (today.getMonth() === birthDate.getMonth() && today.getDate() < birthDate.getDate())
    ) {
        age--;
    }

    ageAttr.setValue(age);
}