Javascript 下拉菜单问题
我正在为学校内部网站写一个下拉菜单,我创造了一个相当奇怪的问题。子菜单与所选菜单y位置偏移36px。 这是代码的摘录(请原谅质量:D)Javascript 下拉菜单问题,javascript,html,css,drop-down-menu,Javascript,Html,Css,Drop Down Menu,我正在为学校内部网站写一个下拉菜单,我创造了一个相当奇怪的问题。子菜单与所选菜单y位置偏移36px。 这是代码的摘录(请原谅质量:D) #纳瓦加通巴尔{ 保证金:0; 填充:0; z指数:30; } #纳瓦加通巴尔{ 列表样式:无; 浮动:左; 字体:粗体12px“Arial”; 左边距:10px; 宽度:96px; } #navagationBar li a{ 显示:块; 边距:0 1px 0; 填充:4px10px; 宽度:136px; 颜色:#FFFFFF; 文本对齐:居中; 文字装饰
#纳瓦加通巴尔{
保证金:0;
填充:0;
z指数:30;
}
#纳瓦加通巴尔{
列表样式:无;
浮动:左;
字体:粗体12px“Arial”;
左边距:10px;
宽度:96px;
}
#navagationBar li a{
显示:块;
边距:0 1px 0;
填充:4px10px;
宽度:136px;
颜色:#FFFFFF;
文本对齐:居中;
文字装饰:无;
}
#navagationBar li a:悬停{
背景:#796952;
}
#navagationBar分区{
位置:绝对位置;
可见性:隐藏;
背景:透明;
}
#navagationBar分区a{
位置:相对位置;
显示:块;
填充物:5px10px;
宽度:136px;
空白:nowrap;
文本对齐:左对齐;
文字装饰:无;
背景:#796952;
颜色:#FFF;
字体:9px“Arial”;
}
#导航条分区a:悬停{
背景:#9696;
颜色:#FFF;
}
#纳瓦加提亚巴酒店{
颜色:#FFF;
}
纳瓦加翁分区{
背景#2d221c;
高度:28px;
}
副处长{
左:156px;
}
var menuItem=0;
var子项=0;
var时限=250;
var closeTimer=0;
var closeSubTimer=0;
//打开菜单
功能菜单(id){
停止计时器();
//如果图层已打开,请将其关闭
如果(菜单项){
menuItem.style.visibility='hidden';
}
//然后将用户单击的一个设置为显示
menuItem=document.getElementById(id);
menuItem.style.visibility='visible';
}
函数openSub(id){
stopSubTimer();
//如果图层已打开,请将其关闭
若有(分项){
subItem.style.visibility='hidden';
}
子项=document.getElementById(id);
subItem.style.visibility='visible';
}
函数关闭(){
如果(菜单项){
menuItem.style.visibility='hidden';
}
}
函数closeSub(){
若有(分项){
subItem.style.visibility='hidden';
}
}
函数startTimer(){
closeTimer=window.setTimeout(关闭,timeLimit);
}
函数startSubTimer(){
closeSubTimer=window.setTimeout(closeSub,timeLimit);
}
//停止计时
函数stopTimer(){
if(关闭计时器){
清除超时(关闭计时器);
closeTimer=null;
}
}
//TODO:使更模块化
函数stopSubTimer(){
if(closeSubTimer){
clearTimeout(closeSubTimer);
closeSubTimer=null;
}
}
//如果用户单击“退出”,请关闭此框
document.onclick=close();
document.onclick=closeSub();
DOM访问
首先,您必须绝对确保不通过getElementbyId()访问DOM代码>在加载整个页面之前
您必须在结束body标记之前调用脚本,或者将整个代码包装在一个函数中,并在结束时,即结束body标记之前调用脚本。这是雅虎!和谷歌前端开发最佳实践
或者,您可以使用JQuery的$(document).ready()函数
或另一个JavaScript库的文档加载函数。然而,使用一个库来解决这个问题未免太过分了
全局变量
通过声明varmenuItem=0代码>在函数范围之外,将变量声明为全局变量,这是一件非常糟糕的事情!它会使整个网站的名称空间变得混乱。在函数内声明变量以创建闭包
此外,您也不希望用整数初始化menuItem变量,因为稍后将引用对象(DOM对象)。尽管Javascript不需要对类型进行dclar,而且这会起作用,但它会给代码的读者带来困惑。只需使用var menuItem代码>在函数内部
CSS块格式上下文
尝试将display:inline
或display:block
与HTML元素一起使用。确保阅读并理解。尝试将子菜单div置于相应的a标记之前(而不是
<html>
<head>
<style>
#navagationBar {
margin: 0;
padding: 0;
z-index: 30;
}
#navagationBar li {
list-style: none;
float: left;
font: bold 12px 'Arial';
margin-left: 10px;
width: 96px;
}
#navagationBar li a {
display: block;
margin: 0 1px 0 0;
padding: 4px 10px;
width: 136px;
color: #FFFFFF;
text-align: center;
text-decoration: none;
}
#navagationBar li a:hover {
background: #796952;
}
#navagationBar div {
position: absolute;
visibility: hidden;
background: transparent;
}
#navagationBar div a {
position: relative;
display: block;
padding: 5px 10px;
width: 136px;
white-space: nowrap;
text-align: left;
text-decoration: none;
background: #796952;
color: #FFF;
font: 9px "Arial";
}
#navagationBar div a:hover {
background: #969696;
color: #FFF;
}
#navagationBar a {
color: #FFF;
}
div.navagation {
background: #2d221c;
height: 28px;
}
div.sub {
left: 156px;
}
</style>
<!-- BG COLOR: #2d221c
FORERGROUND: #3c3429
HOVER: #796952
-->
<script>
var menuItem = 0;
var subItem = 0;
var timeLimit = 250;
var closeTimer = 0;
var closeSubTimer = 0;
// open menu
function openMenu(id) {
stopTimer();
// If a layer is already open close it
if (menuItem) {
menuItem.style.visibility = 'hidden';
}
// Then set the one clicked on by the user to be shown
menuItem = document.getElementById(id);
menuItem.style.visibility = 'visible';
}
function openSub(id) {
stopSubTimer();
// If a layer is already open close it
if (subItem) {
subItem.style.visibility = 'hidden';
}
subItem = document.getElementById(id);
subItem.style.visibility = 'visible';
}
function close() {
if (menuItem) {
menuItem.style.visibility = 'hidden';
}
}
function closeSub() {
if (subItem) {
subItem.style.visibility = 'hidden';
}
}
function startTimer() {
closeTimer = window.setTimeout(close, timeLimit);
}
function startSubTimer() {
closeSubTimer = window.setTimeout(closeSub, timeLimit);
}
// Stop timing
function stopTimer() {
if (closeTimer) {
window.clearTimeout(closeTimer);
closeTimer = null;
}
}
// TODO: Make more modular
function stopSubTimer() {
if (closeSubTimer) {
window.clearTimeout(closeSubTimer);
closeSubTimer = null;
}
}
// If the user click out, close teh box
document.onclick = close();
document.onclick = closeSub();
</script>
</head>
<body>
<div class="navagation">
<ul id="navagationBar">
<li><a href="#" onMouseOver="openMenu('menu0')" onMouseOut="startTimer()">HSIE</a>
<div id="menu0" onMouseOver="stopTimer()" onMouseOut="startTimer()">
<a href="#" onMouseOver="openSub('submenu0_0')" onMouseOut="startSubTimer()">Business Studies</a>
<div class='sub' id="submenu0_0" onMouseOver="openSub('submenu0_0')" onMouseOut="startSubTimer()">
<a href='view.php?id=110'>Year 11</a>
<a href='view.php?id=109'>Year 12</a>
</div>
<a href="#" onMouseOver="openSub('submenu0_1')" onMouseOut="startSubTimer()">Commerce</a>
<div class='sub' id="submenu0_1" onMouseOver="openSub('submenu0_1')" onMouseOut="startSubTimer()">
<a href='view.php?id=112'>Year 9</a>
<a href='view.php?id=111'>Year 10</a>
</div>
<a href="#" onMouseOver="openSub('submenu0_2')" onMouseOut="startSubTimer()">Geography</a>
<div class='sub' id="submenu0_2" onMouseOver="openSub('submenu0_2')" onMouseOut="startSubTimer()">
<a href='view.php?id=48'>Year 7</a>
<a href='view.php?id=92'>Year 8</a>
<a href='view.php?id=105'>Year 9</a>
<a href='view.php?id=70'>Year 10</a>
<a href='view.php?id=69'>Year 11</a>
<a href='view.php?id=131'>Year 12</a>
</div>
<a href="#" onMouseOver="openSub('submenu0_3')" onMouseOut="startSubTimer()">History</a>
<div class='sub' id="submenu0_3" onMouseOver="openSub('submenu0_3')" onMouseOut="startSubTimer()">
<a href='category.php?id=89'>Junior</a>
<a href='category.php?id=90'>Senior</a>
</div>
</div>
</li>
</ul>
</div>
</body>
</html>
<div class='sub' id="submenu0_0" onMouseOver="openSub('submenu0_0')" onMouseOut="startSubTimer()">
<a href='view.php?id=110'>Year 11</a>
<a href='view.php?id=109'>Year 12</a>
</div>
<a href="#" onMouseOver="openSub('submenu0_0')" onMouseOut="startSubTimer()">Business Studies</a>
<a href="#" onMouseOver="openSub('submenu0_0')" onMouseOut="startSubTimer()">Business Studies</a>
<div class='sub' id="submenu0_0" onMouseOver="openSub('submenu0_0')" onMouseOut="startSubTimer()">
<a href='view.php?id=110'>Year 11</a>
<a href='view.php?id=109'>Year 12</a>
</div>
#submenu0_0 > a {top:0px;}
#submenu0_1 > a {top:25px;}
#submenu0_2 > a {top:50px;}
#submenu0_3 > a {top:75px;}
<!DOCTYPE HTML>
<html>
<head>
</head>
<body>
</body>
</html>