function obj(id) {
	return document.getElementById(id);
}
function getElementsByClassName(oElm, strTagName, strClassName){
	var arrElements = (strTagName == "*" && oElm.all)? oElm.all : oElm.getElementsByTagName(strTagName);
	var arrReturnElements = new Array();
	strClassName = strClassName.replace(/\-/g, "\\-");
	var oRegExp = new RegExp("(^|\\s)" + strClassName + "(\\s|$)");
	var oElement;
	for (var i=0; i<arrElements.length; i++) {
		oElement = arrElements[i];
		if (oRegExp.test(oElement.className)) {
			arrReturnElements.push(oElement);
		}
	}
	return (arrReturnElements);
} 
//zobrazi novinku (obrazek, perex) podle id aktuálního elementu
function showNewsById(elementId) {
	var newsItems = getElementsByClassName(obj("news-list"), "div", "news-item");
	var subItemImg, subItemPerex;
	var i;

	if (newsItems.length) {
		newsItemsCount = newsItems.length;
		// schovani vsech polozek - zobrazeni pouze tech, ktere odpovidaji aktualnimu id elementu
		for (i = 0; i < newsItemsCount; i++) {
			subItemImg = getElementsByClassName(newsItems[i],"div","img");
			subItemPerex = getElementsByClassName(newsItems[i],"div","perex");
			if (subItemImg.length) {
			    if ((i+1) == elementId) {
       				subItemImg[0].className = "img";
				}
				else {
       				subItemImg[0].className = "img none";
				}
			}
			if (subItemPerex.length) {
			    if ((i+1) == elementId) {
       				subItemPerex[0].className = "perex";
				}
				else {
       				subItemPerex[0].className = "perex none";
				}
			}
		}
	}
}