window.onload = function(){
	createTab();
	hideHeading();
	showCategory('topics');
	setTabClick('topicsNav','topics');
	setTabClick('economyNav','economy');
	setTabClick('lifeNav','life');
	setTabClick('accidentNav','accident');
	setTabClick('sportsNav','sports');
	setTabClick('seasonNav','season');
	setTabClick('specialNav','special');
};

function hide(elementId) {
	document.getElementById(elementId).style.display = "none";
}
function show(elementId) {
	document.getElementById(elementId).style.display = "block";
}
function hideHeading() {
	hide('topicsheading');
	hide('economyheading');
	hide('lifeheading');
	hide('accidentheading');
	hide('sportsheading');
	hide('seasonheading');
	hide('specialheading');
}


function showCategory(categoryName){
	hide('topics'); 
	hide('economy'); 
	hide('life'); 
	hide('accident'); 
	hide('sports'); 
	hide('season'); 
	hide('special'); 
	show(categoryName);
	changeTab(categoryName);
}


function createTab() {
	var container_newstab = document.getElementById("container_newstab");
	var section_news = document.getElementById("section_news");
	var nav = document.createElement("ul");
	nav.setAttribute('id','nav');
	nav.appendChild(createListItem('topicsNav','#topics','最新ニュース'));
	nav.appendChild(createListItem('economyNav','#economy','経済'));
	nav.appendChild(createListItem('lifeNav','#life','くらし'));
	nav.appendChild(createListItem('accidentNav','#accident','事件・事故'));
	nav.appendChild(createListItem('sportsNav','#sports','スポーツ'));
	nav.appendChild(createListItem('seasonNav','#season','季節'));
	nav.appendChild(createListItem('specialNav','#special','特集'));
	container_newstab.insertBefore(nav,section_news);
}

function createListItem(id,href,text) {
	var li = document.createElement("li");
	var a = document.createElement("a");
	var t = document.createTextNode(text);
	li.setAttribute('id',id);
	a.setAttribute('href',href);
	a.appendChild(t);
	li.appendChild(a);
	return li;
}
function setTabClick(listName,categoryName) {
	var e = document.getElementById(listName).getElementsByTagName('a')[0];
	e.onclick = function(){
		showCategory(categoryName);
		return false;
	};
}

function changeTab(categoryName){
	var e = document.getElementById('nav');
	e.className = categoryName;
}