Javascript下拉菜单不起作用
Javascript Drop Down Menu not working
我正在尝试使用Javascript（没有JQuery）制作下拉菜单。在我的 HTML 中，我有一个包含两个列表项的无序列表，每个列表项包含一个锚点和一个包含更多列表项的无序列表。
我不关心菜单看起来很漂亮，只是担心Javascript可以工作。现在，我正在尝试让它通过while 循环，以便当将鼠标悬停在顶层列表项上时，较低列表项的类将从 CSS 设置为显示的类更改为：none;到具有 display：block 的类;以使它们出现。
我这里只有两个选项卡，但那是因为我从十个选项卡的列表中缩短了它。我也不关心任何进一步的子菜单。
JS小提琴：https://jsfiddle.net/xL5pukd5/
.HTML：
<header>
<!-- <ul> <li><a></a><ul> <li><a></a></li> -->
<!-- dd-menu dd-menu-tab dd-menu-tab-anchor dd-submenu dd-submenu-tab dd-submenu-tab-anchor -->
<nav id="dd-menu-container">
<ul id="dd-menu">
<li class="dd-menu-tab">
<a href="link1.htm" class="dd-menu-tab-anchor" title="Link1">Link 1</a>
<ul class="dd-submenu">
<li class="dd-submenu-tab">
<a href="#" class="dd-submenu-tab-anchor">SubLink1a</a></li>
<li class="dd-submenu-tab">
<a href="#" class="dd-submenu-tab-anchor">Sublink1b</a></li>
</ul>
</li>
<li class="dd-menu-tab">
<a href="link2.htm" class="dd-menu-tab-anchor" title="link2">Link2</a>
<ul class="dd-submenu">
<li class="dd-submenu-tab">
<a href="#" class="dd-submenu-tab-anchor">Sublimn2a</a></li>
<li class="dd-submenu-tab">
<a href="#" class="dd-submenu-tab-anchor">Sublink2b</a></li>
<li class="dd-submenu-tab">
<a href="#" class="dd-submenu-tab-anchor">Sublink2c</a></li>
</ul>
</li>
</nav>
</header>
JavaScript：
getTabs = function(elementClass) {
var tabs = document.getElementsByClassName(elementClass);
return tabs
};
getSubmenus = function(elementClass) {
var submenus = document.getElemenetsByClassName(elementClass);
return submenus;
};
window.onload = function {
var tabs = getTabs("dd-menu-tab");
var submenus = getSubmenus("dd-submenu");
var tabNumber = tabs.length - 1;
var currentTab = 0;
while (currentTab <= tabNumber) {
tabs[currentTab].onmouseover = function {
submenus[currentTab].className = "dd-submenu-onmouseover"
};
tabs[currentTab].onmouseout = function {
submenus[curenetTab].className = "dd-submenu"
};
currentTab += 1;
}
};
.CSS：
.dd-submenu {
display: none;
}
.dd-submenu-onmouseover {
display: block;
}
我尝试使用其他预先编写的下拉菜单方法，但我无法让它们工作，所以我尝试创建自己的方法。提前感谢任何帮助:)
您的脚本存在多个问题，包括注释中提到的拼写错误以及在循环中错误使用闭包变量。
但是你真的不需要js来解决这个问题，你可以使用:hover css选择器来做到这一点
html,
body {
margin: 0;
padding: 0;
}
nav {
display: block;
padding: 0px;
margin: 0;
top: 0;
left: 0;
width: 100%;
background-color: beige;
}
.dd-menu-tab-anchor {
display: inline-block;
color: white;
}
.dd-menu {
position: absolute;
width: 100%;
top: 0;
left: 0;
}
.dd-menu-tab {
float: left;
padding-top: 10px;
padding-bottom: 10px;
padding-left: auto;
padding-right: auto;
width: 9%;
text-align: center;
}
.dd-submenu {
display: none;
}
.dd-menu-tab:hover .dd-submenu {
display: block;
}
li {
list-style-type: none;
background-color: #3300FF;
border: 2px;
border-color: white;
}
a {
text-align: center;
}<header>
<!-- <ul> <li><a></a><ul> <li><a></a></li> -->
<!-- dd-menu dd-menu-tab dd-menu-tab-anchor dd-submenu dd-submenu-tab dd-submenu-tab-anchor -->
<nav id="dd-menu-container">
<ul id="dd-menu">
<li id="dd-menu-tab1" class="dd-menu-tab">
<a href="link1.htm" class="dd-menu-tab-anchor" title="Link1">Link 1</a>
<ul id="dd-submenu1" class="dd-submenu">
<li id="dd-submenu1-tab1" class="dd-submenu-tab">
<a href="link2" id="dd-menu-tab-anchor" class="">SubLink1a</a>
</li>
<li id="dd-submenu1-tab2" class="dd-submenu-tab">
<a href="" id="" class="">Sublink1b</a>
</li>
</ul>
</li>
<li id="dd-menu-tab2" class="dd-menu-tab">
<a href="link2.htm" id="link2" class="dd-menu-tab-anchor" title="link2">Link2</a>
<ul id="dd-submenu2" class="dd-submenu">
<li id="dd-submenu2-tab1" class="dd-submenu-tab">
<a href="#" id="#" class="dd-submenu-tab-anchor">Sublimn2a</a>
</li>
<li id="dd-submenu2-tab2" class="dd-submenu-tab">
<a href="#" id="#" class="dd-submenu-tab-anchor">Sublink2b</a>
</li>
<li id="dd-submenu2-tab3" class="dd-submenu-tab">
<a href="#" id="#" class="dd-submenu-tab-anchor">Sublink2c</a>
</li>
</ul>
</li>
</nav>
</header>
<div>
<h1 id="site title">Website.com</h1>
</div>
<body>
<p>First paragraph sample text</p>
<p>Second paragraph sample text</p>
<p>Third paragraph sample text</p>
</body>
<footer>
<p>
References
</p>
<!-- <script src="file.js" type="text/javascript"></script> -->
</footer>
</html>如果您仍想继续使用逻辑
getTabs = function(elementClass) {
var tabs = document.getElementsByClassName(elementClass);
console.log(tabs);
return tabs
};
getSubmenus = function(elementClass) {
var submenus = document.getElementsByClassName(elementClass);
console.log(submenus);
return submenus;
};
window.onload = function() {
var tabs = getTabs("dd-menu-tab");
var submenus = getSubmenus("dd-submenu");
var tabNumber = tabs.length - 1;
var currentTab = 0;
[].forEach.call(tabs, function(el, idx) {
var submenu = submenus[idx];
el.addEventListener('mouseenter', function() {
submenu.className = "dd-submenu-onmouseover"
});
el.addEventListener('mouseleave', function() {
submenu.className = "dd-submenu"
});
})
};html,
body {
margin: 0;
padding: 0;
}
nav {
display: block;
padding: 0px;
margin: 0;
top: 0;
left: 0;
width: 100%;
background-color: beige;
}
.dd-menu-tab-anchor {
display: inline-block;
color: white;
}
.dd-menu {
position: absolute;
width: 100%;
top: 0;
left: 0;
}
.dd-menu-tab {
float: left;
padding-top: 10px;
padding-bottom: 10px;
padding-left: auto;
padding-right: auto;
width: 9%;
text-align: center;
}
.dd-submenu {
display: none;
}
.dd-submenu-onmouseover {
display: block;
}
li {
list-style-type: none;
background-color: #3300FF;
border: 2px;
border-color: white;
}
a {
text-align: center;
}<header>
<!-- <ul> <li><a></a><ul> <li><a></a></li> -->
<!-- dd-menu dd-menu-tab dd-menu-tab-anchor dd-submenu dd-submenu-tab dd-submenu-tab-anchor -->
<nav id="dd-menu-container">
<ul id="dd-menu">
<li id="dd-menu-tab1" class="dd-menu-tab">
<a href="link1.htm" class="dd-menu-tab-anchor" title="Link1">Link 1</a>
<ul id="dd-submenu1" class="dd-submenu">
<li id="dd-submenu1-tab1" class="dd-submenu-tab">
<a href="link2" id="dd-menu-tab-anchor" class="">SubLink1a</a>
</li>
<li id="dd-submenu1-tab2" class="dd-submenu-tab">
<a href="" id="" class="">Sublink1b</a>
</li>
</ul>
</li>
<li id="dd-menu-tab2" class="dd-menu-tab">
<a href="link2.htm" id="link2" class="dd-menu-tab-anchor" title="link2">Link2</a>
<ul id="dd-submenu2" class="dd-submenu">
<li id="dd-submenu2-tab1" class="dd-submenu-tab">
<a href="#" id="#" class="dd-submenu-tab-anchor">Sublimn2a</a>
</li>
<li id="dd-submenu2-tab2" class="dd-submenu-tab">
<a href="#" id="#" class="dd-submenu-tab-anchor">Sublink2b</a>
</li>
<li id="dd-submenu2-tab3" class="dd-submenu-tab">
<a href="#" id="#" class="dd-submenu-tab-anchor">Sublink2c</a>
</li>
</ul>
</li>
</nav>
</header>
<div>
<h1 id="site title">Website.com</h1>
</div>
<body>
<p>First paragraph sample text</p>
<p>Second paragraph sample text</p>
<p>Third paragraph sample text</p>
</body>
<footer>
<p>
References
</p>
</footer>演示：小提琴
getTabs = function(elementClass) {
var tabs = document.getElementsByClassName(elementClass);
console.log(tabs);
return tabs
};
getSubmenus = function(elementClass) {
var submenus = document.getElemenetsByClassName(elementClass);
console.log(submenus);
return submenus;
};
window.onload = function {
var tabs = getTabs("dd-menu-tab");
var submenus = getSubmenus("dd-submenu");
var tabNumber = tabs.length - 1;
var currentTab = 0;
while (currentTab <= tabNumber) {
tabs[currentTab].onmouseover = function {
submenus[currentTab].className = "dd-submenu-onmouseover"
};
tabs[currentTab].onmouseout = function {
submenus[curenetTab].className = "dd-submenu"
};
currentTab += 1;
}
};html,
body {
margin: 0;
padding: 0;
}
nav {
display: block;
padding: 0px;
margin: 0;
top: 0;
left: 0;
width: 100%;
background-color: beige;
}
.dd-menu-tab-anchor {
display: inline-block;
color: white;
}
.dd-menu {
position: absolute;
width: 100%;
top: 0;
left: 0;
}
.dd-menu-tab {
float: left;
padding-top: 10px;
padding-bottom: 10px;
padding-left: auto;
padding-right: auto;
width: 9%;
text-align: center;
}
.dd-submenu {
display: none;
}
.dd-menu-tab:hover .dd-submenu {
position:absolute;
display: block;
}
li {
list-style-type: none;
background-color: #3300FF;
border: 2px;
border-color: white;
}
a {
text-align: center;
}<header>
<!-- <ul> <li><a></a><ul> <li><a></a></li> -->
<!-- dd-menu dd-menu-tab dd-menu-tab-anchor dd-submenu dd-submenu-tab dd-submenu-tab-anchor -->
<nav id="dd-menu-container">
<ul id="dd-menu">
<li id="dd-menu-tab1" class="dd-menu-tab">
<a href="link1.htm" class="dd-menu-tab-anchor" title="Link1">Link 1</a>
<ul id="dd-submenu1" class="dd-submenu">
<li id="dd-submenu1-tab1" class="dd-submenu-tab">
<a href="link2" id="dd-menu-tab-anchor" class="">SubLink1a</a></li>
<li id="dd-submenu1-tab2" class="dd-submenu-tab">
<a href="" id="" class="">Sublink1b</a></li>
</ul>
</li>
<li id="dd-menu-tab2" class="dd-menu-tab">
<a href="link2.htm" id="link2" class="dd-menu-tab-anchor" title="link2">Link2</a>
<ul id="dd-submenu2" class="dd-submenu">
<li id="dd-submenu2-tab1" class="dd-submenu-tab">
<a href="#" id="#" class="dd-submenu-tab-anchor">Sublimn2a</a></li>
<li id="dd-submenu2-tab2" class="dd-submenu-tab">
<a href="#" id="#" class="dd-submenu-tab-anchor">Sublink2b</a></li>
<li id="dd-submenu2-tab3" class="dd-submenu-tab">
<a href="#" id="#" class="dd-submenu-tab-anchor">Sublink2c</a></li>
</ul>
</li>
</nav>
</header>
<div>
<h1 id="site title">Website.com</h1>
</div>
<body>
<p>First paragraph sample text</p>
<p>Second paragraph sample text</p>
<p>Third paragraph sample text</p>
</body>
<footer>
<p>
References
</p>
<!-- <script src="file.js" type="text/javascript"></script> -->
</footer>
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