jQuery implements switching page transition animation effect

<main>
 <p class="cd-index cd-main-content">
  <p>
   <h1>Page Transition</h1>
   <!-- your content here -->
  </p>
 </p>
</main>
 
<p class="cd-cover-layer"></p> <!-- this is the cover layer -->
 
<p class="cd-loading-bar"></p> <!-- this is the loading bar -->

CSS style

The page switching effects use body::before and body:: The after pseudo-element creates two mask layers to cover the page content during page switching. Their positioning is fixed, with a height equal to 50vh and a width of 100%. By default, they are hidden using the CSS transform property (translateY(-100%)/translateY(100%)). When the user switches pages, these elements are moved back into the viewport (by adding the .page-is-changing class to the element).
The following picture demonstrates this process:

Page switching special effects

body::after, body::before {
 /* these are the 2 half blocks which cover the content once the animation is triggered */
 height: 50vh;
 width: 100%;
 position: fixed;
 left: 0;
}
body::before {
 top: 0;
 transform: translateY(-100%);
}
body::after {
 bottom: 0;
 transform: translateY(100%);
}
body.page-is-changing::after, body.page-is-changing::before {
 transform: translateY(0);
}

When the page is switched, the fade-in and fade-out effect of the page content is achieved by changing the transparency of p.cd-cover-layer. It overlays the .cd-main-content element with the same background color, and then changes the transparency from 0 to 1 when the is added with the .page-is-changing class.
Loading progress bar is made using .cd-loading-bar::before pseudo-element. By default it is scaled down (scaleX(0)) and transform-origin: left center. When the page switch begins it is enlarged to its original size using scaleX(1).

.cd-loading-bar {
 /* this is the loading bar - visible while switching from one page to the following one */
 position: fixed;
 height: 2px;
 width: 90%;
}
.cd-loading-bar::before {
 /* this is the progress bar inside the loading bar */
 position: absolute;
 left: 0;
 top: 0;
 height: 100%;
 width: 100%;
 transform: scaleX(0);
 transform-origin: left center;
}
.page-is-changing .cd-loading-bar::before {
 transform: scaleX(1);
}

The smooth transition effect in special effects is achieved using CSS Transitions. Different transition-delays are added to each animated element to achieve different element animation sequences.
JAVASCRIPT

The data-type="page-transition" attribute is used on the link in this page switching effect to trigger the page switching event. When the plug-in detects a user click event, the changePage() method will be executed.

$('main').on('click', '[data-type="page-transition"]', function(event){
  event.preventDefault();
  //detect which page has been selected
  var newPage = $(this).attr('href');
  //if the page is not animating - trigger animation
  if( !isAnimating ) changePage(newPage, true);
});

This method will trigger the page switching animation and load new content through the loadNewContent() method.

function changePage(url, bool) {
  isAnimating = true;
  // trigger page animation
  $('body').addClass('page-is-changing');
  //...
  loadNewContent(url, bool);
  //...
}

When the new content is loaded, it will replace the content in the original

function loadNewContent(url, bool) {
  var newSectionName = 'cd-'+url.replace('.html', ''),
   section = $(&#39;<p class="cd-main-content &#39;+newSectionName+&#39;"></p>&#39;);
    
  section.load(url+&#39; .cd-main-content > *&#39;, function(event){
   // load new content and replace <main> content with the new one
    $(&#39;main&#39;).html(section);
    //...
    $(&#39;body&#39;).removeClass(&#39;page-is-changing&#39;);
    //...
 
    if(url != window.location){
     //add the new page to the window.history
     window.history.pushState({path: url},&#39;&#39;,url);
    }
 });
}

$(window).on('popstate', function() {
  var newPageArray = location.pathname.split('/'),
    //this is the url of the page to be loaded 
    newPage = newPageArray[newPageArray.length - 1];
  if( !isAnimating ) changePage(newPage);
});