function fadeInPage() {

    if (!window.AnimationEvent) { return; }

    let contentFader = document.getElementById('content-fader');
    let sidebarFader = document.getElementById('sidebar-fader');

    contentFader.classList.add('fade-out');
    sidebarFader.classList.add('fade-out');
}

document.addEventListener(“DOMContentLoaded”, function() {

if (!window.AnimationEvent) { return; }

let links = document.getElementsByClassName("fade-onclick");
for (let i = 0; i < links.length; i += 1) {
    links[i].addEventListener("click", function(event) {
        let contentFader = document.getElementById("content-fader"),
            sidebarFader = document.getElementById("sidebar-fader"),
            anchor = event.currentTarget;

        let listener = function() {
            window.location = anchor.href;
            contentFader.removeEventListener("animationend", listener);
            sidebarFader.removeEventListener("animationend", listener);
        };
        contentFader.addEventListener("animationend", listener);
        sidebarFader.addEventListener("animationend", listener);

        event.preventDefault();
        contentFader.classList.add("fade-in");
        sidebarFader.classList.add("fade-in");
    });
}

});

// Remove class in case of page being cached, add class for page navigation through means other than links (eg refresh, back/forward) window.addEventListener(“pageshow”, function (event) {

if (!event.persisted) {
    return;
}
let contentFader = document.getElementById("content-fader");
let sidebarFader = document.getElementById("sidebar-fader");

contentFader.classList.remove("fade-in");
sidebarFader.classList.remove("fade-in");

contentFader.classList.add("fade-out");
sidebarFader.classList.add("fade-out");

});