MktoForms2 :: Suppress form on close/success

HTML

<script src="//app-aba.marketo.com/js/forms2/js/forms2.min.js"></script>

<form id="mktoForm_1043"></form>

<script>
var mktoInstance = '//app-aba.marketo.com',
    munchkinId = '648-VJF-461',
    formId = 1043,
    formHideCookie = 'mktoForm_hide_'+formId+'=1';

    
if ( !cookieExists(formHideCookie) ) {
    MktoForms2.loadForm(mktoInstance, munchkinId, formId,
    function (form){
        var formEl = form.getFormElem()[0],        
            lightbox = MktoForms2.lightbox(form).show(),
            closeEl = document.querySelector('.mktoModalClose');
    
        closeEl.onclick = function(e){
            hideFormForSession();        
        };    
    
        form.onSuccess(function(){
            hideFormForSession();
            lightbox.hide();   
            return false;
        });
    
    });
 }

function cookieExists(cookieKV){
    return new RegExp('(^|;| )'+cookieKV+'(;|$)').test(document.cookie)
}
   
function hideFormForSession(){
    document.cookie = formHideCookie+';expires=-1';
}

</script>