var sbPage = 1;

function docGet(name){
    return document.getElementById(name);
}

function pageForward(table, maxItems, hasHeader) {               
    var tblSb = docGet(table);
    var rows = tblSb.getElementsByTagName("tr");
    var arrElm = new Array();
    for (var i = 0; i < rows.length; i++) {
        arrElm[i] = rows[i];
    }
    arrElm.pop();
    if(hasHeader) arrElm.shift();
    if(sbPage >= arrElm.length) return;
    var lastItem = sbPage + maxItems;
    if(lastItem > arrElm.length) {
        lastItem = arrElm.length;
        sbPage = lastItem - maxItems;
    }
    for (var i = 0; i < arrElm.length; i++) arrElm[i].style.display = 'none';
    for (var i = sbPage; i < lastItem; i++) arrElm[i].style.display = '';
    sbPage = lastItem;
    if(sbPage > arrElm.length) sbPage -= arrElm.length;
}

function pageBack(table, maxItems, hasHeader) {
    if(sbPage < 1) {
        sbPage = 1;
        return;
    }
    var tblSb = docGet(table);
    var rows = tblSb.getElementsByTagName("tr");
    var arrElm = new Array();
    for (var i = 0; i < rows.length; i++) {
        arrElm[i] = rows[i];
    }
    arrElm.pop();    
    if(hasHeader) arrElm.shift();
    var firstItem = sbPage - maxItems;
    if(firstItem < 0) {
        firstItem = 0;
        sbPage = firstItem + maxItems;
    }
    for (var i = 0; i < arrElm.length; i++) arrElm[i].style.display = 'none';
    for (var i = firstItem; i < sbPage; i++) arrElm[i].style.display = '';
    sbPage = firstItem;
}