$$plugins.define('lazyload', function (element, options) {
    const plugin = this;
    plugin.logger.debug("lazy loading");
    const mutationObserver =
            new MutationObserver(function (mutations) {
                mutations.forEach(function (mutation, index) {
                    if (mutation.type === 'childList') {
                        mutation.addedNodes.forEach(update);
                    }
                });
            }),
        observer =
            new IntersectionObserver(function (entries, self) {
                entries.forEach(function (entry) {
                    if (entry.isIntersecting) {
                        load(entry.target);
                        self.unobserve(entry.target);
                    }
                });
            }, options || {
                rootMargin: '0px 0px 1250px 0px',
                threshold: 0
            }),
        elms = element.querySelectorAll('.lazy');
    elms.forEach(elm => observer.observe(elm));
    mutationObserver.observe(element, { childList: true, subtree: true });

    function update(element) {
        if (!(element instanceof (HTMLElement))) {
            return;
        }
        const container = element || document;
        if (!container.querySelectorAll) {
            return;
        }
        const elms = container.querySelectorAll('.lazy');
        Array.prototype.forEach.call(elms, (elm) => !elm.getAttribute('data-loaded') && observer.observe(elm));
    }

    function load(elm) {
        let i = 0, source, attr, picture = elm.parentElement, sources = picture.querySelectorAll('.lazysrcset');
        if (sources.length) {
            for (; i < sources.length; i++) {
                source = sources[i];
                attr = source.getAttribute('data-srcset');
                if (attr) {
                    source.srcset = source.getAttribute('data-srcset');
                }
            }
        }

        if (!elm.getAttribute('data-loaded') && elm.getAttribute('data-src')) {
            elm.src = elm.getAttribute('data-src');
            elm.setAttribute('data-loaded', true);
        }
    }

    return {
        update: update
    };
});