function checkCheckboxes() {
    elems = document.getElementsByTagName('input');

    for(var i = 0; i < elems.length; i++) {
        if (elems[i].type == "checkbox" && elems[i].checked) {
            return true;
        }
    }
    alert("Geen event geselecteerd.");
    return false
}

function validateUserForm() {
    var errors = "De volgende velden zijn verplicht: ";
    var error_cnt = 0;
    
    if (document.getElementById("attendee_initials").value == "") {
        if (error_cnt > 0)
            errors += ", ";
        errors += "Voorletter(s)";
        error_cnt += 1;
    }
    if (document.getElementById("attendee_last_name").value == "") {
        if (error_cnt > 0)
            errors += ", ";
        errors += "Achternaam";
        error_cnt += 1;
    }
    if (document.getElementById("attendee_address").value == "") {
        if (error_cnt > 0)
            errors += ", ";
        errors += "Adres";
        error_cnt += 1;
    }
    if (document.getElementById("attendee_postal_code").value == "") {
        if (error_cnt > 0)
            errors += ", ";
        errors += "Postcode";
        error_cnt += 1;
    }
    if (document.getElementById("attendee_city").value == "") {
        if (error_cnt > 0)
            errors += ", ";
        errors += "Plaats";
        error_cnt += 1;
    }
    if (document.getElementById("attendee_email").value == "") {
        if (error_cnt > 0)
            errors += ", ";
        errors += "E-mail adres";
        error_cnt += 1;
    }
    if (error_cnt > 0) {
        alert(errors);
        return false;
    }
    
    return true;
}

function displayEmailSettings() {
    document.getElementById("displaybutton").style.display = "none";
    document.getElementById("emailsettings").innerHTML = "The following email settings are global settings and can be overwritten by group specific settings."
    elems = document.getElementsByTagName("tr");

    for(var i = 0; i < elems.length; i++) {
        if (elems[i].className == "emailsetting") {
            elems[i].style.display = "table-row";
        }
    }
}