本文實例講述了JavaScript實作箭頭識別的多層下拉式選單效果。分享給大家供大家參考。具體如下：
這是一個支援多級顯示的JS選單，滑鼠移向有小三角的選單項，可下拉出二級子選單項，在該主選單的上方會顯示標記，指引當前的位置，本選單程式碼使用了一個JS類，可依程式碼位址自行下載，這個選單未在網路上測試，用在自己的網站裡可能要修改程式碼。
運作效果截圖如下：
線上示範網址如下：
http://demo.jb51.net/js/2015/js-focus-m-select-menu-nav-codes/
具體程式碼如下：
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>多级展开的横向菜单</title>
<!--[imcss] *** Infinite Menus Core CSS: Keep this section in the document head for full validation. -->
<style type="text/css">.imcm ul,.imcm li,.imcm div,.imcm span,.imcm a{text-align:left;vertical-align:top;padding:0px;margin:0;list-style:none outside none;border-style:none;background-image:none;clear:none;float:none;display:block;position:static;overflow:visible;line-height:normal;}.imcm li a img{display:inline;border-width:0px;}.imcm span{display:inline;}.imcm .imclear,.imclear{clear:both;height:0px;visibility:hidden;line-height:0px;font-size:1px;}.imcm .imsc{position:relative;}.imcm .imsubc{position:absolute;visibility:hidden;}.imcm li{list-style:none;font-size:1px;float:left;}.imcm ul ul li{width:100%;float:none !important;}.imcm a{display:block;position:relative;}.imcm ul .imsc,.imcm ul .imsubc {z-index:10;}.imcm ul ul .imsc,.imcm ul ul .imsubc{z-index:20;}.imcm ul ul ul .imsc,.imcm ul ul ul .imsubc{z-index:30;}.imde ul li:hover .imsubc{visibility:visible;}.imde ul ul li:hover .imsubc{visibility:visible;}.imde ul ul ul li:hover .imsubc{visibility:visible;}.imde li:hover ul .imsubc{visibility:hidden;}.imde li:hover ul ul .imsubc{visibility:hidden;}.imde li:hover ul ul ul .imsubc{visibility:hidden;}.imcm .imea{display:block;position:relative;left:0px;font-size:1px;line-height:1px;height:0px;width:1px;float:right;}.imcm .imea span{display:block;position:relative;font-size:1px;line-height:0px;}.dvs,.dvm{border-width:0px}/*\*//*/.imcm .imea{visibility:hidden;}/**/</style><!--[if IE]><style type="text/css">.imcm .imea span{position:absolute;}.imcm .imclear,.imclear{display:none;}.imcm{zoom:1;} .imcm li{curosr:hand;} .imcm ul{zoom:1}.imcm a{zoom:1;}</style><![endif]--><!--[if gte IE 7]><style type="text/css">.imcm .imsubc{background-image:url(ie_css_fix);}</style><![endif]--><!--end-->
<!--[imstyles] *** Infinite Menu Styles: Keep this section in the document head for full validation. -->
<style type="text/css">
#imenus0 .imeam span,#imenus0 .imeamj span {background-image:url(images/sample3_main_arrow.gif); width:7px; height:5px; left:-7px; top:5px; background-repeat:no-repeat;background-position:top left;}
#imenus0 li:hover .imeam span,#imenus0 li a.iactive .imeamj span {background-image:url(images/sample3_main_arrow.gif); background-repeat:no-repeat;background-position:top left;}
#imenus0 ul .imeas span,#imenus0 ul .imeasj span {background-image:url(images/sample3_sub_arrow.gif); width:5px; height:7px; left:-5px; top:3px; background-repeat:no-repeat;background-position:top left;}
#imenus0 ul li:hover .imeas span,#imenus0 ul li a.iactive .imeasj span {background-image:url(images/sample3_sub_arrow.gif); background-repeat:no-repeat;background-position:top left;}
#imouter0 {background-color:#ffffff; border-style:none; border-color:#6a6a6a; border-width:1px; padding:0px; margin:0px; }
#imenus0 li ul {background-color:#efefef; border-style:solid; border-color:#cccccc; border-width:1px; padding:5px; margin:4px 0px 0px; }
#imenus0 li a, #imenus0 .imctitle {color:#333333; text-align:left; font-family:Arial; font-size:12px; font-weight:normal; text-decoration:underline; border-style:solid; border-color:#dddddd; border-width:1px; padding:2px 8px; }
#imenus0 li:hover>a {background-color:#efefef; text-decoration:underline; }
#imenus0 li a.ihover, .imde imenus0 a:hover {background-color:#efefef; text-decoration:underline; }
#imenus0 li a.iactive {}
#imenus0 ul a, #imenus0 .imsubc li .imctitle {color:#555555; text-align:left; font-size:11px; font-weight:normal; text-decoration:none; border-style:none; border-color:#000000; border-width:1px; padding:2px 5px; }
#imenus0 ul li:hover>a {color:#000000; text-decoration:underline; }
#imenus0 ul li a.ihover {color:#000000; text-decoration:underline; }
#imenus0 ul li a.iactive {background-color:#ffffff; }
</style><!--end-->
</head>
<body>
<div class="imrcmain0 imgl" style="width:580px;z-index:999999;position:relative;"><div class="imcm imde" id="imouter0"><ul id="imenus0">
<li class="imatm" style="width:145px;"><a class="" href="#"><span class="imea imeam"><span></span></span>Who We Are</a>
<div class="imsc"><div class="imsubc" style="width:145px;top:0px;left:0px;"><ul >
<li><a href="#">Overview</a></li>
<li><a href="#">Mission & Goals</a></li>
<li><a href="#">History</a></li>
<li><a href="#">Management</a></li>
<li><a href="#">Working at Tyco</a></li>
<li><a href="#">Press Center</a></li>
<li><a href="#"><span class="imea imeas"><span></span></span>Worldwide</a>
<div class="imsc"><div class="imsubc" style="width:140px;top:-23px;left:132px;"><ul >
<li><a href="#">Europe</a></li>
<li><a href="#">Asia</a></li>
<li><a href="#">US & Canada</a></li>
<li><a href="#">Mexico</a></li>
<li><a href="#">Australia</a></li>
<li><a href="#">Middle East</a></li>
</ul></div></div></li>
<li><a href="#"><span class="imea imeas"><span></span></span>Board of Directors</a>
<div class="imsc"><div class="imsubc" style="width:140px;top:-23px;left:132px;"><ul >
<li><a href="#">Overview</a></li>
<li><a href="#">Electronics</a></li>
<li><a href="#">Fire & Security</a></li>
<li><a href="#">Healthcare</a></li>
<li><a href="#">Plastics & Adhesives</a></li>
<li><a href="#">Engineered Producs</a></li>
<li><a href="#">Tyco Worldwide</a></li>
</ul></div></div></li>
<li><a href="#">Customers</a></li>
</ul></div></div></li>
<li class="imatm" style="width:145px;"><a href="#"><span class="imea imeam"><span></span></span>Our Commitment</a>
<div class="imsc"><div class="imsubc" style="width:146px;top:0px;left:-1px;"><ul >
<li><a href="#">Overview</a></li>
<li><a href="#">People & Values</a></li>
<li><a href="#">Governance</a></li>
<li><a href="#">Community</a></li>
<li><a href="#">Environmental</a></li>
</ul></div></div></li>
<li class="imatm" style="width:145px;"><a href="#"><span class="imea imeam"><span></span></span>Our Business</a>
<div class="imsc"><div class="imsubc" style="width:146px;top:0px;left:0px;"><ul >
<li><a href="#">Overview</a></li>
<li><a href="#">Electronics</a></li>
<li><a href="#">Fire & Security</a></li>
<li><a href="#">Healthcare</a></li>
<li><a href="#">Plastics & Adhesives</a></li>
<li><a href="#">Engineered Producs</a></li>
<li><a href="#">Tyco Worldwide</a></li>
</ul></div></div></li>
<li class="imatm" style="width:145px;"><a href="#"><span class="imea imeam"><span></span></span>Investors</a>
<div class="imsc"><div class="imsubc" style="width:146px;top:0px;left:-1px;"><ul >
<li><a href="#">Overview</a></li>
<li><a href="#">Stock Quotes</a></li>
</ul></div></div></li>
</ul><div class="imclear"> </div></div></div>
<script language="JavaScript" src="images/ocscript.js" type="text/javascript"></script>
</body>
</html>
希望本文所述對大家的javascript程式設計有所幫助。
