<script type="text/javascript"> 
function SDMenu(id) { 
    if (!document.getElementById || !document.getElementsByTagName) 
        return false; 
    this.menu = document.getElementById(id); 
    this.submenus = this.menu.getElementsByTagName("div"); 
    this.remember = true; 
    this.speed = 3; 
    this.markCurrent = true; 
    this.oneSmOnly = false; 
} 
SDMenu.prototype.init = function() { 
    var mainInstance = this; 
    for (var i = 0; i < this.submenus.length; i++) 
        this.submenus[i].getElementsByTagName("span")[0].onclick = function() { 
            mainInstance.toggleMenu(this.parentNode); 
        }; 
    if (this.markCurrent) { 
        var links = this.menu.getElementsByTagName("a"); 
        for (var i = 0; i < links.length; i++) 
            if (links[i].href == document.location.href) { 
                links[i].className = "current"; 
                break; 
            } 
    } 
    if (this.remember) { 
        var regex = new RegExp("sdmenu_" + encodeURIComponent(this.menu.id) + "=([01]+)"); 
        var match = regex.exec(document.cookie); 
        if (match) { 
            var states = match[1].split(""); 
            for (var i = 0; i < states.length; i++) 
                this.submenus[i].className = (states[i] == 0 ? "collapsed" : ""); 
        } 
    } 
}; 
SDMenu.prototype.toggleMenu = function(submenu) { 
    if (submenu.className == "collapsed") 
        this.expandMenu(submenu); 
    else 
        this.collapseMenu(submenu); 
}; 
SDMenu.prototype.expandMenu = function(submenu) { 
    var fullHeight = submenu.getElementsByTagName("span")[0].offsetHeight; 
    var links = submenu.getElementsByTagName("a"); 
    for (var i = 0; i < links.length; i++) 
        fullHeight += links[i].offsetHeight; 
    var moveBy = Math.round(this.speed * links.length); 
     
    var mainInstance = this; 
    var intId = setInterval(function() { 
        var curHeight = submenu.offsetHeight; 
        var newHeight = curHeight + moveBy; 
        if (newHeight < fullHeight) 
            submenu.style.height = newHeight + "px"; 
        else { 
            clearInterval(intId); 
            submenu.style.height = ""; 
            submenu.className = ""; 
            mainInstance.memorize(); 
        } 
    }, 30); 
    this.collapseOthers(submenu); 
}; 
SDMenu.prototype.collapseMenu = function(submenu) { 
    var minHeight = submenu.getElementsByTagName("span")[0].offsetHeight; 
    var moveBy = Math.round(this.speed * submenu.getElementsByTagName("a").length); 
    var mainInstance = this; 
    var intId = setInterval(function() { 
        var curHeight = submenu.offsetHeight; 
        var newHeight = curHeight - moveBy; 
        if (newHeight > minHeight) 
            submenu.style.height = newHeight + "px"; 
        else { 
            clearInterval(intId); 
            submenu.style.height = ""; 
            submenu.className = "collapsed"; 
            mainInstance.memorize(); 
        } 
    }, 30); 
}; 
SDMenu.prototype.collapseOthers = function(submenu) { 
    if (this.oneSmOnly) { 
        for (var i = 0; i < this.submenus.length; i++) 
            if (this.submenus[i] != submenu && this.submenus[i].className != "collapsed") 
                this.collapseMenu(this.submenus[i]); 
    } 
}; 
SDMenu.prototype.expandAll = function() { 
    var oldOneSmOnly = this.oneSmOnly; 
    this.oneSmOnly = false; 
    for (var i = 0; i < this.submenus.length; i++) 
        if (this.submenus[i].className == "collapsed") 
            this.expandMenu(this.submenus[i]); 
    this.oneSmOnly = oldOneSmOnly; 
}; 
SDMenu.prototype.collapseAll = function() { 
    for (var i = 0; i < this.submenus.length; i++) 
        if (this.submenus[i].className != "collapsed") 
            this.collapseMenu(this.submenus[i]); 
}; 
SDMenu.prototype.memorize = function() { 
    if (this.remember) { 
        var states = new Array(); 
        for (var i = 0; i < this.submenus.length; i++) 
            states.push(this.submenus[i].className == "collapsed" ? 0 : 1); 
        var d = new Date(); 
        d.setTime(d.getTime() + (30 * 24 * 60 * 60 * 1000)); 
        document.cookie = "sdmenu_" + encodeURIComponent(this.menu.id) + "=" + states.join("") + "; expires=" + d.toGMTString() + "; path=/"; 
    } 
}; 
</script> 
 

 
var myMenu = new SDMenu("main_menu"); // 菜单ID 
 
// 默认参数 
myMenu.speed = 3;                     // 折叠速度 
myMenu.remember = true;               // 是否记录状态 
myMenu.oneSmOnly = false;             // 一次只有一个菜单打开 
myMenu.markCurrent = true;            // 是否高亮当前菜单 
 
myMenu.init(); 
 
// 附加方法 
var firstSubmenu = myMenu.submenus[0]; 
myMenu.expandMenu(firstSubmenu);      // 打开一个菜单 
myMenu.collapseMenu(firstSubmenu);    // 关闭一个菜单 
myMenu.toggleMenu(firstSubmenu);      // 当菜单关闭时打开，当菜单打开时关闭 
 
myMenu.expandAll();                   // 打开所有菜单 
myMenu.collapseAll();                 // 关闭所有菜单