encantar-js/demos/assets/poster.js

(function() {

const IMAGE_PREFIX = '../assets/';
const DEFAULT_IMAGE = 'mage.webp';

const paths = [];
let index = 0;

function changeImage(direction)
{
    index = (index + direction + paths.length) % paths.length;
    document.body.style.backgroundImage = 'url(' + IMAGE_PREFIX + paths[index] + ')';
}

document.addEventListener('DOMContentLoaded', function() {

    const prev = document.getElementById('prev');
    const next = document.getElementById('next');

    const arImages = (document.body.dataset.arImages || DEFAULT_IMAGE).split(';');
    paths.push.apply(paths, arImages);
    changeImage(0);

    if(!prev || !next)
        return;

    prev.addEventListener('click', function() { changeImage(-1); });
    next.addEventListener('click', function() { changeImage(+1); });

    if(paths.length < 2)
        prev.hidden = next.hidden = true;

});

})();