js 通过cookie实现刷新不变化树形菜单

通过设置cookie来保存树形菜单的状态，在页面加载时重新读取cookie来设置菜单。

菜单的HTML结构：

<div class="treemenu"><ul><li><a href="#" id="treemenu_a_1">一级菜单一</a><div class="submenu" id="submenu_1"><ul><li><a href="subpage/a.html" id="submenu_a_1_1">二级菜单一</a></li><li><a href="subpage/b.html" id="submenu_a_1_2">二级菜单二</a></li><li><a href="#" id="submenu_a_1_3">二级菜单三</a></li><li><a href="#" id="submenu_a_1_4">二级菜单四</a></li><li><a href="#" id="submenu_a_1_5">二级菜单五</a></li></ul></div></li><li><a href="#" id="treemenu_a_2">一级菜单二</a><div class="submenu" id="submenu_2"><ul><li><a href="#" id="submenu_a_2_1">二级菜单一</a><div class="submenu" id="submenu_2_1"><ul><li><a href="#" id="submenu_a_2_1_1">三级菜单一</a></li><li><a href="#" id="submenu_a_2_1_2">三级菜单二</a></li><li><a href="#" id="submenu_a_2_1_3">三级菜单三</a><div class="submenu" id="submenu_2_1_3"><ul><li><a href="#" id="submenu_a_2_1_3_1">四级菜单一</a></li><li><a href="#" id="submenu_a_2_1_3_2">四级菜单二</a></li><li><a href="#" id="submenu_a_2_1_3_3">四级菜单三</a></li></ul></div></li></ul></div></li><li><a href="#" id="submenu_a_2_2">二级菜单二</a></li><li><a href="#" id="submenu_a_2_3">二级菜单三</a></li><li><a href="#" id="submenu_a_2_4">二级菜单四</a></li><li><a href="#" id="submenu_a_2_5">二级菜单五</a></li></ul></div></li><li><a href="#" id="treemenu_a_3">一级菜单三</a><div class="submenu" id="submenu_3"><ul><li><a href="#" id="submenu_a_3_1">二级菜单一</a></li><li><a href="#" id="submenu_a_3_2">二级菜单二</a></li><li><a href="#" id="submenu_a_3_3">二级菜单三</a></li><li><a href="#" id="submenu_a_3_4">二级菜单四</a></li><li><a href="#" id="submenu_a_3_5">二级菜单五</a></li></ul></div></li></ul></div>

读取cookie工具类：

//cookie工具类var cookieTool = {//读取cookiegetCookie: function(c_name) {if (document.cookie.length > 0) {c_start = document.cookie.indexOf(c_name + "=");if (c_start != -1) {c_start = c_start + c_name.length + 1;c_end = document.cookie.indexOf(";", c_start);if (c_end == -1) {c_end = document.cookie.length;}return unescape(document.cookie.substring(c_start, c_end));}}return "";},//设置cookiesetCookie: function(c_name, value, expiredays) {var exdate = new Date();exdate.setDate(exdate.getDate() + expiredays); //设置日期document.cookie = c_name + "=" + escape(value) + ((expiredays == null) ? "" : ";expires=" + exdate.toGMTString());},//删除cookiedelCookie: function(c_name) {var exdate = new Date();exdate.setDate(exdate.getDate() - 1); //昨天日期document.cookie = c_name + "=;expires=" + exdate.toGMTString();}};