function $(id){
	return document.getElementById(id);
	}
/*** cookie ***/
function init() {
    var cur = getCookie('cur_menu');
	if(cur!='') expandIt(cur);
}
function setCookie(name, value) {
     document.cookie = name + "=" + escape(value);
}


function getCookie(Name) {
    var search = Name + "="
    if(document.cookie.length > 0) {
     offset = document.cookie.indexOf(search)
     if(offset != -1) {
         offset += search.length
         end = document.cookie.indexOf(";", offset)
         if(end == -1) end = document.cookie.length
         return unescape(document.cookie.substring(offset, end))
     }
     else return ""
    }
}
/**************/
function expandIt(el) {
	var count=0;//做计数器
	var limit=new Array();//用于记录当前显示的哪几个菜单
	var countlimit=1;//同时打开菜单数目，可自定义
	var obj = $("sub" + el);
	if (obj.style.display == "none") {
		obj.style.display = "block";//显示子菜单
		setCookie('cur_menu',el);
		if (count<countlimit) {//限制2个
		limit[count]=el;//录入数组
		count++;
		}
		else {
		$("sub" + limit[0]).style.display = "none";
		for (i=0;i<limit.length-1;i++) {limit[i]=limit[i+1];}//数组去掉头一位，后面的往前挪一位
		limit[limit.length-1]=el;
		}
	}
	else {
	obj.style.display = "none";
	var j=0;
	for (i=0;i<limit.length;i++) {if (limit[i]==el) j=i;}//获取当前点击的菜单在limit数组中的位置
	for (i=j;i<limit.length-1;i++) {limit[i]=limit[i+1];}//j以后的数组全部往前挪一位
	limit[limit.length-1]=null;//删除数组最后一位
	count--;
	}
}


window.onload=init;