用户通过点击页面左侧的菜单，对应的页面加载时伴随着滑动过滤动画，并带有进度条效果。当然页面的加载是Ajax驱动的，整个加载过渡过程非常流畅，非常好的用户体验。
HTML
HTML结构中，.cd-main包含页面主体内容，.cd-side-navigation包含着侧边导航条，#cd-loading-bar则是用来做进度条动画用的。
<nav class="cd-side-navigation">
<ul>
<li>
<a href="index.html" class="selected" data-menu="index">
<svg><!-- svg content here --></svg>
Intro
</a>
</li>
<li>
<!-- ... -->
</li>
<!-- other list items here -->
</ul>
</nav> <!-- .cd-dashboard -->
<main class="cd-main">
<section class="cd-section index visible">
<header>
<div class="cd-title">
<h2>Animated Page Transition #2</h2>
<span>Some text here</span>
</div>
<a href="#index-content" class="cd-scroll">Scroll Down</a>
</header>
<div class="cd-content" id="index-content">
<!-- content here -->
</div> <!-- .cd-content -->
</section> <!-- .cd-section -->
</main> <!-- .cd-main -->
<div id="cd-loading-bar" data-scale="1" class="index"></div> <!-- lateral loading bar -->
CSS
我们将.cd-side-navigation固定在页面左侧，并且设置它的高度为100%，这样左侧导航菜单就始终占据左侧边栏，右侧主体内容滚动时，左侧导航菜单不动。
.cd-side-navigation {
position: fixed;
z-index: 3;
top: 0;
left: 0;
height: 100vh;
width: 94px;
overflow: hidden;
}
.cd-side-navigation ul {
height: 100%;
overflow-y: auto;
}
.cd-side-navigation::before {
/* background color of the side navigation */
content: '';
position: absolute;
top: 0;
left: 0;
height: 100%;
width: calc(100% - 4px);
background-color: #131519;
}
.cd-side-navigation li {
width: calc(100% - 4px);
}
.cd-side-navigation a {
display: block;
position: relative;
}
.cd-side-navigation a::after {
/* 4px line to the right of the item - visible on hover */
content: '';
position: absolute;
top: 0;
right: -4px;
height: 100%;
width: 4px;
background-color: #83b0b9;
opacity: 0;
}
.no-touch .cd-side-navigation a:hover::after {
opacity: 1;
}
JavaScript
当我们点击左侧菜单时，调用triggerAnimation()函数，这个函数会触发加载进度条动画函数loadingBarAnimation()，接着加载页面内容函数：loadNewContent()。
function loadingBarAnimation() {
var scaleMax = loadingBar.data('scale');
if( scaleY + 1 < scaleMax) {
newScaleValue = scaleY + 1;
}
// ...
loadingBar.velocity({
scaleY: newScaleValue
}, 100, loadingBarAnimation);
}
当新页面被选中时，一个新的元素.cd-section将会被创建并且插入到DOM中，然后load()新的url内容。
function loadNewContent(newSection) {
var section = $('<section class="cd-section overflow-hidden '+newSection+'"></section>').appendTo(mainContent);
//load the new content from the proper html file
section.load(newSection+'.html .cd-section > *', function(event){
loadingBar.velocity({
scaleY: scaleMax //this is the scaleY value to cover the entire window height (100% loaded)
}, 400, function(){
section.addClass('visible');
var url = newSection+'.html';
if(url!=window.location){
//add the new page to the window.history
window.history.pushState({path: url},'',url);
}
// ...
});
});
}
通过异步加载的页面要返回上一页历史浏览记录的话，可以点击浏览器上的返回即可。返回上一页同样有过渡动画效果。
