基于JS快速实现导航下拉菜单动画效果附源码下载

<header class="cd-morph-dropdown"> 
<a href="#0" class="nav-trigger">Open Nav<span aria-hidden="true"></span></a> 
<nav class="main-nav"> 
<ul> 
<li class="has-dropdown gallery" data-content="about"> 
<a href="#0">About</a> 
</li> 
<li class="has-dropdown links" data-content="pricing"> 
<a href="#0">Pricing</a> 
</li> 
<li class="has-dropdown button" data-content="contact"> 
<a href="#0">Contact</a> 
</li> 
</ul> 
</nav> 
<div class="morph-dropdown-wrapper"> 
<div class="dropdown-list"> 
<ul> 
<li id="about" class="dropdown gallery"> 
<!-- dropdown content here --> 
</li> 
<li id="pricing" class="dropdown links"> 
<!-- dropdown content here --> 
</li> 
<li id="contact" class="dropdown button"> 
<!-- dropdown content here --> 
</li> 
</ul> 
<div class="bg-layer" aria-hidden="true"></div> 
</div> <!-- dropdown-list --> 
</div> <!-- morph-dropdown-wrapper --> 
</header>

function morphDropdown( element ) { 
this.element = element; 
this.mainNavigation = this.element.find('.main-nav'); 
this.mainNavigationItems = this.mainNavigation.find('.has-dropdown'); 
this.dropdownList = this.element.find('.dropdown-list'); 
//... 
this.bindEvents(); 
}
bindEvents()方法用于在.has-dropdown和.dropdown元素上检测鼠标进入和鼠标离开事件。
morphDropdown.prototype.bindEvents = function() { 
var self = this; 
this.mainNavigationItems.mouseenter(function(event){ 
//hover over one of the nav items -> show dropdown 
self.showDropdown($(this)); 
}).mouseleave(function(){ 
//if not hovering over a nav item or a dropdown -> hide dropdown 
if( self.mainNavigation.find('.has-dropdown:hover').length == 0 && self.element.find('.dropdown-list:hover').length == 0 ) self.hideDropdown(); 
}); 
//... 
}; 
showDropdown方法用于处理宽度、高度和.dropdown-list元素的translateX值，以及放大和缩小.bg-layer元素。
morphDropdown.prototype.showDropdown = function(item) { 
var selectedDropdown = this.dropdownList.find('#'+item.data('content')), 
selectedDropdownHeight = selectedDropdown.innerHeight(), 
selectedDropdownWidth = selectedDropdown.children('.content').innerWidth(), 
selectedDropdownLeft = item.offset().left + item.innerWidth()/2 - selectedDropdownWidth/2; 
//update dropdown and dropdown background position and size 
this.updateDropdown(selectedDropdown, parseInt(selectedDropdownHeight), selectedDropdownWidth, parseInt(selectedDropdownLeft)); 
//add the .active class to the selected .dropdown and .is-dropdown-visible to the .cd-morph-dropdown 
//... 
}; 
morphDropdown.prototype.updateDropdown = function(dropdownItem, height, width, left) { 
this.dropdownList.css({ 
'-moz-transform': 'translateX(' + left + 'px)', 
'-webkit-transform': 'translateX(' + left + 'px)', 
'-ms-transform': 'translateX(' + left + 'px)', 
'-o-transform': 'translateX(' + left + 'px)', 
'transform': 'translateX(' + left + 'px)', 
'width': width+'px', 
'height': height+'px' 
}); 
this.dropdownBg.css({ 
'-moz-transform': 'scaleX(' + width + ') scaleY(' + height + ')', 
'-webkit-transform': 'scaleX(' + width + ') scaleY(' + height + ')', 
'-ms-transform': 'scaleX(' + width + ') scaleY(' + height + ')', 
'-o-transform': 'scaleX(' + width + ') scaleY(' + height + ')', 
'transform': 'scaleX(' + width + ') scaleY(' + height + ')' 
}); 
};