滑动式折叠菜单 － Slashdot’s Menu

折叠菜单让你在尽可能小的地方放置尽可能多的内容，同时加大了操作的简便性，因此，深受前台设计师的喜爱。随着大家对动画效果的钟爱，折叠菜单也开始“动”起来了，本文介绍的就是 DimX 制作的滑动式折叠菜单效果－Slashdot’s Menu。

滑动式折叠菜单 － Slashdot’s Menu – 示例

<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>

调用方式

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