var timeOut  = 4000;
var currItem = 0;
var timerId  = null;



function showNewsItem() {
  document.getElementById('back').onclick = buttonClick;
  document.getElementById('next').onclick = buttonClick;
  setText();
}

function buttonClick(e) {
  if (this.id == "back") {
    prevArticle();
  } else if (this.id == "next") {
    nextArticle();
  }
}

function prevArticle() {
  clearTimeout(timerId);
  currItem = currItem - 2;
  if(currItem < 0)
    currItem = 0;
  setText();
}

function nextArticle() {
  clearTimeout(timerId);  
  currItem++;
  if(currItem >= arrNewsItems.length) 
    currItem = 0;
  setText();
}

function setText() {
  var tickElem = document.getElementById("tick");  
  var tickFirstChild =  tickElem.firstChild;
  
  var tickLinkElem = document.createElement("a");
  tickLinkElem.setAttribute('href', arrNewsItems[currItem][1]);
  tickLinkElem.setAttribute('target', '_top');
  tickText = document.createTextNode(arrNewsItems[currItem][0]);
  tickLinkElem.appendChild(tickText);
  tickElem.replaceChild(tickLinkElem,tickFirstChild);
  
  currItem++;
  if(currItem >= arrNewsItems.length - 1)
    currItem = 0;
  timerId = setTimeout('setText()',timeOut);
}

showNewsItem();