$(document).ready(function () {
    $("[name='onderwerp']").keyup(function () {
        var onderwerp = document.forms.contactformulier.onderwerp.value;
        if (onderwerp === null || onderwerp === "") {
            $("#onderwerp").fadeIn(800);
        } else {
            $("#onderwerp").hide(800);
        }
    });
    $("[name='email']").keyup(function () {
        var email, atpos, dotpos;
        email = document.forms.contactformulier.email.value;
        atpos = email.indexOf("@");
        dotpos = email.lastIndexOf(".");
        if (atpos < 1 || dotpos < atpos + 2 || dotpos + 2 >= email.length) {
            $("#email").fadeIn(800);
        } else {
            $("#email").hide(800);
        }
    });
});
function submitCheck() {
    var email, atpos, dotpos, onderwerp;
    email = document.forms.contactformulier.email.value;
    atpos = email.indexOf("@");
    dotpos = email.lastIndexOf(".");
    onderwerp = document.forms.contactformulier.onderwerp.value;
    if (atpos < 1 || dotpos < atpos + 2 || dotpos + 2 >= email.length) {
        $("#email").show();
    }
    if (onderwerp === "") {
        $("#onderwerp").show();
    }
    if (onderwerp === "" || email === "") {
        alert("Gelieve het inschrijvingsformulier correct in te vullen");
        return false;
    }
}