.constructor === Array)
}
function nextitm()
{
    if(lastleftitem!=null)
    {
        let sib = lastleftitem.nextSibling;
        if(sib)
        {
            clickItem(sib);
        }
    }
}
function clickItem(titleDiv)
{
    let index = titleDiv.getAttribute('data-index');
    const contentsDiv = document.getElementById('contents');
    lastselectedidx = index;
    contentsDiv.innerHTML = renderPage(db[index],true).text;
    contentsDiv.scrollTop = 0;
    if (lastleftitem) {
     