css +js制作下拉菜单教程

作者：袖梨 2022-07-02

提示：您可以先修改部分代码再运行

/* SpryMenuBarVertical.css - Revision: Spry Preview Release 1.4 */

/*******************************************************************************

LAYOUT INFORMATION: describes box model, positioning, z-order

*******************************************************************************/

/* The outermost container of the Menu Bar, a fixed width box with no margin or padding */
ul.MenuBarVertical
{
	margin: 0;
	padding: 0;
	list-style-type: none;
	font-size: 100%;
	cursor: default;
	width: 8em;
}
/* Set the active Menu Bar with this class, currently setting z-index to accomodate IE rendering bug: http://therealcrisp.xs4all.nl/meuk/IE-zindexbug.html */
ul.MenuBarActive
{
	z-index: 1000;
}
/* Menu item containers, position children relative to this container and are same fixed width as parent */
ul.MenuBarVertical li
{
	margin: 0;
	padding: 0;
	list-style-type: none;
	font-size: 100%;
	position: relative;
	text-align: left;
	cursor: pointer;
	width: 8em;
}
/* Submenus should appear slightly overlapping to the right (95%) and up (-5%) with a higher z-index, but they are initially off the left side of the screen (-1000em) */
ul.MenuBarVertical ul
{
	margin: -5% 0 0 95%;
	padding: 0;
	list-style-type: none;
	font-size: 100%;
	position: absolute;
	z-index: 1020;
	cursor: default;
	width: 8.2em;
	left: -1000em;
	top: 0;
}
/* Submenu that is showing with class designation MenuBarSubmenuVisible, we set left to 0 so it comes onto the screen */
ul.MenuBarVertical ul.MenuBarSubmenuVisible
{
	left: 0;
}
/* Menu item containers are same fixed width as parent */
ul.MenuBarVertical ul li
{
	width: 8.2em;
}

/*******************************************************************************

DESIGN INFORMATION: describes color scheme, borders, fonts

*******************************************************************************/

/* Outermost menu container has borders on all sides */
ul.MenuBarVertical
{
	border: 1px solid #CCC;
}
/* Submenu containers have borders on all sides */
ul.MenuBarVertical ul
{
	border: 1px solid #CCC;
}
/* Menu items are a light gray block with padding and no text decoration */
ul.MenuBarVertical a
{
	display: block;
	cursor: pointer;
	background-color: #EEE;
	padding: 0.5em 0.75em;
	color: #333;
	text-decoration: none;
}
/* Menu items that have mouse over or focus have a blue background and white text */
ul.MenuBarVertical a:hover, ul.MenuBarVertical a:focus
{
	background-color: #33C;
	color: #FFF;
}
/* Menu items that are open with submenus are set to MenuBarItemHover with a blue background and white text */
ul.MenuBarVertical a.MenuBarItemHover, ul.MenuBarVertical a.MenuBarItemSubmenuHover, ul.MenuBarVertical a.MenuBarSubmenuVisible
{
	background-color: #33C;
	color: #FFF;
}

/*******************************************************************************

SUBMENU INDICATION: styles if there is a submenu under a given menu item

*******************************************************************************/

/* Menu items that have a submenu have the class designation MenuBarItemSubmenu and are set to use a background image positioned on the far left (95%) and centered vertically (50%) */
ul.MenuBarVertical a.MenuBarItemSubmenu
{
	background-image: url(SpryMenuBarRight.gif);
	background-repeat: no-repeat;
	background-position: 95% 50%;
}

/* Menu items that are open with submenus have the class designation MenuBarItemSubmenuHover and are set to use a "hover" background image positioned on the far left (95%) and centered vertically (50%) */
ul.MenuBarVertical a.MenuBarItemSubmenuHover
{
	background-image: url(SpryMenuBarRightHover.gif);
	background-repeat: no-repeat;
	background-position: 95% 50%;
}

/*******************************************************************************

BROWSER HACKS: the hacks below should not be changed unless you are an expert

*******************************************************************************/

/* HACK FOR IE: to make sure the sub menus show above form controls, we underlay each submenu with an iframe */
ul.MenuBarVertical iframe
{
	position: absolute;
	z-index: 1010;
}
/* HACK FOR IE: to stabilize appearance of menu items; the slash in float is to keep IE 5.0 from parsing */
@media screen, projection
{
	ul.MenuBarVertical li.MenuBarItemIE
	{
		display: inline;
		float: left;
		background: #FFF;
	}
}

</style>

// Constructor for Menu Bar
// element should be an ID of an unordered list (<ul> tag)
// preloadImage1 and preloadImage2 are images for the rollover state of a menu
Spry.Widget.MenuBar = function(element, opts)
{
	this.init(element, opts);
};

Spry.Widget.MenuBar.prototype.init = function(element, opts)
{
	this.element = this.getElement(element);

// represents the current (sub)menu we are operating on
	this.currMenu = null;

var isie = (typeof document.all != 'undefined' && typeof window.opera == 'undefined' && navigator.vendor != 'KDE');
	if(typeof document.getElementById == 'undefined' || (navigator.vendor == 'Apple Computer, Inc.' && typeof window.XMLHttpRequest == 'undefined') || (isie && typeof document.uniqueID == 'undefined'))
	{
		// bail on older unsupported browsers
		return;
	}

// load hover images now
	if(opts)
	{
		for(var k in opts)
		{
			var rollover = new Image;
			rollover.src = opts[k];
		}
	}

if(this.element)
	{
		this.currMenu = this.element;
		var items = this.element.getElementsByTagName('li');
		for(var i=0; i<items.length; i++)
		{
			this.initialize(items[i], element, isie);
			if(isie)
			{
				this.addClassName(items[i], "MenuBarItemIE");
				items[i].style.position = "static";
			}
		}
		if(isie)
		{
			if(this.hasClassName(this.element, "MenuBarVertical"))
			{
				this.element.style.position = "relative";
			}
			var linkitems = this.element.getElementsByTagName('a');
			for(var i=0; i<linkitems.length; i++)
			{
				linkitems[i].style.position = "relative";
			}
		}
	}
};

Spry.Widget.MenuBar.prototype.getElement = function(ele)
{
	if (ele && typeof ele == "string")
		return document.getElementById(ele);
	return ele;
};

Spry.Widget.MenuBar.prototype.hasClassName = function(ele, className)
{
	if (!ele || !className || !ele.className || ele.className.search(new RegExp("b" + className + "b")) == -1)
	{
		return false;
	}
	return true;
};

Spry.Widget.MenuBar.prototype.addClassName = function(ele, className)
{
	if (!ele || !className || this.hasClassName(ele, className))
		return;
	ele.className += (ele.className ? " " : "") + className;
};

Spry.Widget.MenuBar.prototype.removeClassName = function(ele, className)
{
	if (!ele || !className || !this.hasClassName(ele, className))
		return;
	ele.className = ele.className.replace(new RegExp("s*b" + className + "b", "g"), "");
};

// addEventListener for Menu Bar
// attach an event to a tag without creating obtrusive HTML code
Spry.Widget.MenuBar.prototype.addEventListener = function(element, eventType, handler, capture)
{
	try
	{
		if (element.addEventListener)
		{
			element.addEventListener(eventType, handler, capture);
		}
		else if (element.attachEvent)
		{
			element.attachEvent('on' + eventType, handler);
		}
	}
	catch (e) {}
};

// createIframeLayer for Menu Bar
// creates an IFRAME underneath a menu so that it will show above form controls and ActiveX
Spry.Widget.MenuBar.prototype.createIframeLayer = function(menu)
{
	var layer = document.createElement('iframe');
	layer.tabIndex = '-1';
	layer.src = 'javascript:false;';
	menu.parentNode.appendChild(layer);
	
	layer.style.left = menu.offsetLeft + 'px';
	layer.style.top = menu.offsetTop + 'px';
	layer.style.px';
	layer.style.px';
};

// removeIframeLayer for Menu Bar
// removes an IFRAME underneath a menu to reveal any form controls and ActiveX
Spry.Widget.MenuBar.prototype.removeIframeLayer =  function(menu)
{
	var layers = menu.parentNode.getElementsByTagName('iframe');
	while(layers.length > 0)
	{
		layers[0].parentNode.removeChild(layers[0]);
	}
};

// clearMenus for Menu Bar
// root is the top level unordered list (<ul> tag)
Spry.Widget.MenuBar.prototype.clearMenus = function(root)
{
	var menus = root.getElementsByTagName('ul');
	for(var i=0; i<menus.length; i++)
	{
		this.hideSubmenu(menus[i]);
	}
	this.removeClassName(this.element, "MenuBarActive");
};

// bubbledTextEvent for Menu Bar
// identify bubbled up text events in Safari so we can ignore them
Spry.Widget.MenuBar.prototype.bubbledTextEvent = function()
{
	return (navigator.vendor == 'Apple Computer, Inc.' && (event.target == event.relatedTarget.parentNode || (event.eventPhase == 3 && event.target.parentNode == event.relatedTarget)));
};

// showSubmenu for Menu Bar
// set the proper CSS class on this menu to show it
Spry.Widget.MenuBar.prototype.showSubmenu = function(menu)
{
	if(this.currMenu)
	{
		this.clearMenus(this.currMenu);
		this.currMenu = null;
	}
	
	if(menu)
	{
		this.addClassName(menu, "MenuBarSubmenuVisible");
		if(typeof document.all != 'undefined' && typeof window.opera == 'undefined' && navigator.vendor != 'KDE')
		{
			if(!this.hasClassName(this.element, "MenuBarHorizontal") || menu.parentNode.parentNode != this.element)
			{
				menu.style.top = menu.parentNode.offsetTop + 'px';
			}
		}
		if(typeof document.uniqueID != "undefined")
		{
			this.createIframeLayer(menu);
		}
	}
	this.addClassName(this.element, "MenuBarActive");
};

// hideSubmenu for Menu Bar
// remove the proper CSS class on this menu to hide it
Spry.Widget.MenuBar.prototype.hideSubmenu = function(menu)
{
	if(menu)
	{
		this.removeClassName(menu, "MenuBarSubmenuVisible");
		if(typeof document.all != 'undefined' && typeof window.opera == 'undefined' && navigator.vendor != 'KDE')
		{
			menu.style.top = '';
			menu.style.left = '';
		}
		this.removeIframeLayer(menu);
	}
};

// initialize for Menu Bar
// create event listeners for the Menu Bar widget so we can properly
// show and hide submenus
Spry.Widget.MenuBar.prototype.initialize = function(listitem, element, isie)
{
	var opentime, closetime;
	var link = listitem.getElementsByTagName('a')[0];
	var submenus = listitem.getElementsByTagName('ul');
	var menu = (submenus.length > 0 ? submenus[0] : null);

var hasSubMenu = false;
	if(menu)
	{
		this.addClassName(link, "MenuBarItemSubmenu");
		hasSubMenu = true;
	}

if(!isie)
	{
		// define a simple function that comes standard in IE to determine
		// if a node is within another node
		listitem.contains = function(testNode)
		{
			// this refers to the list item
			if(testNode == null)
			{
				return false;
			}
			if(testNode == this)
			{
				return true;
			}
			else
			{
				return this.contains(testNode.parentNode);
			}
		};
	}
	
	// need to save this for scope further down
	var self = this;

this.addEventListener(listitem, 'mouseover', function(e)
	{
		if(self.bubbledTextEvent())
		{
			// ignore bubbled text events
			return;
		}
		clearTimeout(closetime);
		if(self.currMenu == listitem)
		{
			self.currMenu = null;
		}
		// show menu highlighting
		self.addClassName(link, hasSubMenu ? "MenuBarItemSubmenuHover" : "MenuBarItemHover");
		if(menu && !self.hasClassName(menu, "MenuBarSubmenuVisible"))
		{
			opentime = window.setTimeout(function(){self.showSubmenu(menu);}, 250);
		}
	}, false);

this.addEventListener(listitem, 'mouseout', function(e)
	{
		if(self.bubbledTextEvent())
		{
			// ignore bubbled text events
			return;
		}

var related = (typeof e.relatedTarget != 'undefined' ? e.relatedTarget : e.toElement);
		if(!listitem.contains(related))
		{
			clearTimeout(opentime);
			self.currMenu = listitem;

// remove menu highlighting
			self.removeClassName(link, hasSubMenu ? "MenuBarItemSubmenuHover" : "MenuBarItemHover");
			if(menu)
			{
				closetime = window.setTimeout(function(){self.hideSubmenu(menu);}, 600);
			}
		}
	}, false);
};

</script>
<link href="SpryAssets/SpryMenuBarVertical.css" rel="stylesheet" type="text/css">
<body>
<ul id="MenuBar1" class="MenuBarVertical">
  <li><a class="MenuBarItemSubmenu" href="#">项目 1</a>
      <ul>
        <li><a href="#">项目 1.1</a></li>
        <li><a href="#">项目 1.2</a></li>
        <li><a href="#">项目 1.3</a></li>
      </ul>
  </li>
  <li><a href="#">项目 2</a></li>
  <li><a class="MenuBarItemSubmenu" href="#">项目 3</a>
      <ul>
        <li><a class="MenuBarItemSubmenu" href="#">项目 3.1</a>
            <ul>
              <li><a href="#">项目 3.1.1</a></li>
              <li><a href="#">项目 3.1.2</a></li>
            </ul>
        </li>
        <li><a href="#">项目 3.2</a></li>
        <li><a href="#">项目 3.3</a></li>
      </ul>
  </li>
  <li><a href="#">项目 4</a></li>
</ul>

<script type="text/javascript">

</script>
</body>

提示：您可以先修改部分代码再运行

css +js制作下拉菜单教程

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