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通過設置cookie來保存樹形菜單的狀態，在頁面加載時重新讀取cookie來設置菜單。

菜單的HTML結構：

<div class="treemenu">
<ul>
<li>
<a href="#" id="treemenu_a_1">一級菜單一</a>
<div class="submenu" id="submenu_1">
<ul>
<li><a href="subpage/a.html" id="submenu_a_1_1">二級菜單一</a></li>
<li><a href="subpage/b.html" id="submenu_a_1_2">二級菜單二</a></li>
<li><a href="#" id="submenu_a_1_3">二級菜單三</a></li>
<li><a href="#" id="submenu_a_1_4">二級菜單四</a></li>
<li><a href="#" id="submenu_a_1_5">二級菜單五</a></li>
</ul>
</div>
</li>
<li>
<a href="#" id="treemenu_a_2">一級菜單二</a>
<div class="submenu" id="submenu_2">
<ul>
<li>
<a href="#" id="submenu_a_2_1">二級菜單一</a>
<div class="submenu" id="submenu_2_1">
<ul>
<li><a href="#" id="submenu_a_2_1_1">三級菜單一</a></li>
<li><a href="#" id="submenu_a_2_1_2">三級菜單二</a></li>
<li>
<a href="#" id="submenu_a_2_1_3">三級菜單三</a>
<div class="submenu" id="submenu_2_1_3">
<ul>
<li><a href="#" id="submenu_a_2_1_3_1">四級菜單一</a></li>
<li><a href="#" id="submenu_a_2_1_3_2">四級菜單二</a></li>
<li><a href="#" id="submenu_a_2_1_3_3">四級菜單三</a></li>
</ul>
</div>
</li>
</ul>
</div>
</li>
<li><a href="#" id="submenu_a_2_2">二級菜單二</a></li>
<li><a href="#" id="submenu_a_2_3">二級菜單三</a></li>
<li><a href="#" id="submenu_a_2_4">二級菜單四</a></li>
<li><a href="#" id="submenu_a_2_5">二級菜單五</a></li>
</ul>
</div>
</li>
<li>
<a href="#" id="treemenu_a_3">一級菜單三</a>
<div class="submenu" id="submenu_3">
<ul>
<li><a href="#" id="submenu_a_3_1">二級菜單一</a></li>
<li><a href="#" id="submenu_a_3_2">二級菜單二</a></li>
<li><a href="#" id="submenu_a_3_3">二級菜單三</a></li>
<li><a href="#" id="submenu_a_3_4">二級菜單四</a></li>
<li><a href="#" id="submenu_a_3_5">二級菜單五</a></li>
</ul>
</div>
</li>
</ul>
</div>

讀取cookie工具類：

//cookie工具類
var cookieTool = {
//讀取cookie
getCookie: 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 "";
},
//設置cookie
setCookie: function(c_name, value, expiredays) {
var exdate = new Date();
exdate.setDate(exdate.getDate() + expiredays); //設置日期
document.cookie = c_name + "=" + escape(value) + ((expiredays == null) ? "" : ";expires=" + exdate.toGMTString());
},
//刪除cookie
delCookie: function(c_name) {
var exdate = new Date();
exdate.setDate(exdate.getDate() - 1); //昨天日期
document.cookie = c_name + "=;expires=" + exdate.toGMTString();
}
};

菜單事件綁定：

//菜單事件綁定
$('.treemenu a').bind('click', function() {
var $this = $(this);
var id = $this.attr('id');
var $submenu = $this.next('.submenu');
if ($submenu.length > 0) { //是否有子菜單
var flag = $(this).next('.submenu:hidden').length > 0 ? true : false;
if (flag) {
$submenu.show();
} else {
$submenu.hide();
}
var display = flag ? 'block' : 'none';
cookieTool.setCookie(id, display, 10);
} else {
cookieTool.setCookie(id, id, 10);
var curId = cookieTool.getCookie(id);
$('.treemenu').find('.on').removeClass('on').addClass('off');
$('#' + curId).addClass('on');
$('.treemenu a[class="off"]').each(function() { 
cookieTool.delCookie($(this).attr('id')); //刪除其他已選擇選項cookie
});
}
});

頁面加載時重新設置菜單

//頁面加載讀取cookies
$('.treemenu a').each(function() {
showMenu($(this).attr('id'));
});

//讀取cookie顯示菜單
function showMenu(id) {
var $this = $('#' + id);
var cookie = cookieTool.getCookie(id);
if (cookie) {
if ($this.next('.submenu').length > 0) {
$this.next('.submenu').css('display', cookie);
} else {
$('#' + cookie).addClass('on');
}
}
}

完整DEMO：

【JavaScript】刷新不變化樹形菜單(多級菜單).zip

注意：chrome本地控制台無法讀取cookie，需要在firefox/IE或者服務器環境下測試