// collect all element Ids
var nkiLabelElementId = 'nki-label';
var nkiFlashElementId = 'product-intro';
var nkiNoFlashElementId = 'product-intro-noflash';
var nkiShowFlash = true;

// collect element objects
var nkiFlashElement = document.getElementById(nkiFlashElementId);

// copy current alternative flash text element
// the element is overwritten by the flash content
// and the action cannot be underdone.
// This workaround copies the element to a parallel hidden element
// that will be displayed by toggleFlash()
var nkiEl = document.createElement('div');
    nkiEl.id = nkiNoFlashElementId;
    nkiEl.innerHTML = nkiFlashElement.innerHTML;
    nkiEl.style.display = 'none';
    
// append
nkiFlashElement.parentNode.appendChild(nkiEl);
var nkiNotFlashElement = document.getElementById(nkiNoFlashElementId);

// var nkiDataFlash = '';
// var nkiDataNoFlash = nkiFlashElement.innerHTML;

function nkiToggleInputLabel(flashenabled) {
    var el = document.getElementById(nkiLabelElementId);
    var label = flashenabled ? 'Disattiva flash' : 'Attiva flash';
    
    el.innerHTML = label;
}

function nkiToggleFlash() {
    nkiShowFlash = !nkiShowFlash;
    nkiFlashElement.style.display       = nkiShowFlash ? 'block' : 'none';
    nkiNotFlashElement.style.display    = nkiShowFlash ? 'none' : 'block';
    nkiToggleInputLabel(nkiShowFlash);
}

// run onload
nkiToggleInputLabel(true);