本文给大家分享一段实例代码关于js实现下拉菜单功能，具体代码如下所示：
<!doctype html> <html lang="en"> <head> <meta charset="UTF-8"> <title>下拉菜单</title> <style type="text/css"> body, ul, li { margin: 0; padding: 0; font-size: 13px; } ul, li { list-style: none; } #divselect { width: 186px; margin: 80px auto; position: relative; z-index: 10000; } #divselect cite { width: 150px; height: 24px; line-height: 24px; display: block; color: #807a62; cursor: pointer; font-style: normal; padding-left: 4px; padding-right: 30px; border: 1px solid #333333; /*background: url(xjt.png) no-repeat right center;*/ } cite:before { content: ''; position: absolute; right: 7px; bottom: 7px; width: 0; height: 0; border-width: 4px; border-style: solid; border-color: #888 transparent transparent transparent; transition: all 0.2s; -webkit-transition: all 0.2s; -moz-transition: all 0.2s; -o-transition: all 0.2s; -ms-transition: all 0.2s; transform-origin: 50% 25%; -ms-transform-origin: 50% 25%; -moz-transform-origin: 50% 25%; -webkit-transform-origin: 50% 25%; -o-transform-origin: 50% 25%; } .extended cite:before { transform: rotate(180deg); -webkit-transform: rotate(180deg); -moz-transform: rotate(180deg); -o-transform: rotate(180deg); -ms-transform: rotate(180deg); } #divselect ul { width: 184px; border: 1px solid #333333; background-color: #ffffff; position: absolute; z-index: 20000; margin-top: -1px; display: none; } #divselect ul li { height: 24px; line-height: 24px; } #divselect ul li a { display: block; height: 24px; color: #333333; text-decoration: none; padding-left: 10px; padding-right: 10px; } .animated { animation-fill-mode: both; -webkit-animation-fill-mode: both; -moz-animation-fill-mode: both; -o-animation-fill-mode: both; -ms-animation-fill-mode: both; } .speed_fast { animation-duration: .3s; /*-webkit-animation-duration: 0.2s; -moz-animation-duration: 0.2s; -o-animation-duration: 0.2s; -ms-animation-duration: 0.2s;*/ } .anim_extendDown { animation-name: extendDown; -webkit-animation-name: extendDown; -moz-animation-name: extendDown; -o-animation-name: extendDown; -ms-animation-name: extendDown; } @keyframes extendDown { 0% { border-bottom-color: transparent; height: 0; } 100% { border-bottom-color: #333; height: 120px; } } @-webkit-keyframes extendDown { 0% { border-bottom-color: transparent; height: 0; } 100% { border-bottom-color: #333; height: 120px; } } @-moz-keyframes extendDown { 0% { border-bottom-color: transparent; height: 0; } 100% { border-bottom-color: #333; height: 120px; } } @-o-keyframes extendDown { 0% { border-bottom-color: transparent; height: 0; } 100% { border-bottom-color: #333; height: 120px; } } @-ms-keyframes extendDown { 0% { border-bottom-color: transparent; height: 0; } 100% { border-bottom-color: #333; height: 120px; } } </style> </head> <body> <div id="divselect"> <cite>请选择分类</cite> <ul> <li id="li"> <a href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" selectid="1">ASP开发</a> </li> <li> <a href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" selectid="2">.NET开发</a> </li> <li> <a href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" selectid="3">PHP开发</a> </li> <li> <a href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" selectid="4">Javascript开发</a> </li> <li> <a href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" selectid="5">Java特效</a> </li> </ul> </div> <script type="text/javascript"> window.onload = function() { var box = document.getElementById('divselect'), title = box.getElementsByTagName('cite')[0], menu = box.getElementsByTagName('ul')[0], as = box.getElementsByTagName('a'), index = -1; //初始样式 function resetM() { box.className = ""; menu.className = ""; menu.style.display = "none"; index = -1; resetA(); } //清空a选项样式 function resetA() { for(var i = 0; i < as.length; i++) { as[i].style.background = "#fff"; } } // 点击三角时 title.onclick = function(event) { //阻止事件冒泡 event = event || window.event; event.stopPropagation ? event.stopPropagation() : event.cancelBubble = true; if(box.className == "extended") { resetM(); } else { box.className = "extended"; //给box加类名让三角旋转 menu.className = "animated speed_fast anim_extendDown"; //下拉菜单的下拉动画 menu.style.display = "block"; } } document.onkeydown = function(event) { event = event || window.event; if(box.className == "extended") { if(event.keyCode == 38) { //向上键 event.preventDefault ? event.preventDefault() : event.returnValue = false; index--; if(index == -1) { index = as.length - 1; } resetA(); as[index].style.background = "#ccc"; } else if(event.keyCode == 40) { //向下键 event.preventDefault ? event.preventDefault() : event.returnValue = false; index++; if(index == as.length) { index = 0; } resetA(); as[index].style.background = "#ccc"; } else if(event.keyCode == 13) { //回车键 event.preventDefault ? event.preventDefault() : event.returnValue = false; title.innerHTML = as[index].innerHTML; resetM(); } } } // 滑过滑过、离开、点击每个选项时 for(var i = 0; i < as.length; i++) { as[i].onmouseover = function() { resetA(); this.style.background = "#ccc"; index = this.getAttribute('selectid') - 1; } as[i].onclick = function() { resetM(); title.innerHTML = this.innerHTML; } } // 点击页面空白处时 document.onclick = function() { resetM(); } } </script> </body> </html> 1、要阻止事件冒泡
2、键盘事件，用index索引
3、通过设置类名或清空类名的方式给元素增加动画和恢复原有样式
以上所述是小编给大家介绍的JavaScript下拉菜单功能实例代码，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对武林网网站的支持！
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