本文給大家分享一段實例代碼關于js實現下拉菜單功能，具體代碼如下所示：
<!doctype html> <html lang="en"> <head> <meta charset="UTF-8"> <title>下拉菜單</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>請選擇分類</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開發</a> </li> <li> <a href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" selectid="2">.NET開發</a> </li> <li> <a href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" selectid="3">PHP開發</a> </li> <li> <a href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" selectid="4">Javascript開發</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; //初始樣式 function resetM() { box.className = ""; menu.className = ""; menu.style.display = "none"; index = -1; resetA(); } //清空a選項樣式 function resetA() { for(var i = 0; i < as.length; i++) { as[i].style.background = "#fff"; } } // 點擊三角時 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"; //給box加類名讓三角旋轉 menu.className = "animated speed_fast anim_extendDown"; //下拉菜單的下拉動畫 menu.style.display = "block"; } } document.onkeydown = function(event) { event = event || window.event; if(box.className == "extended") { if(event.keyCode == 38) { //向上鍵 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) { //向下鍵 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) { //回車鍵 event.preventDefault ? event.preventDefault() : event.returnValue = false; title.innerHTML = as[index].innerHTML; resetM(); } } } // 滑過滑過、離開、點擊每個選項時 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; } } // 點擊頁面空白處時 document.onclick = function() { resetM(); } } </script> </body> </html> 1、要阻止事件冒泡
2、鍵盤事件，用index索引
3、通過設置類名或清空類名的方式給元素增加動畫和恢復原有樣式
以上所述是小編給大家介紹的JavaScript下拉菜單功能實例代碼，希望對大家有所幫助，如果大家有任何疑問請給我留言，小編會及時回復大家的。在此也非常感謝大家對武林網網站的支持！
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