lazyload.js

((document, window) => {
    document.addEventListener('DOMContentLoaded', () => {
        let images = Array.from(document.querySelectorAll('img[data-src]'));

        if (!('IntersectionObserver' in window)) {
            images.forEach(image => {
                image.src = image.dataset.src;
            });
        } else {
            let observer = new IntersectionObserver((entries, observer) => {
                entries.forEach(entry => {
                    if (entry.intersectionRatio > 0) {
                        let image = entry.target;

                        observer.unobserve(image);
                        image.src = image.dataset.src;
                    }
                });
                
            }, {rootMargin: '50px 0px', threshold: 0.01});

            images.forEach(image => observer.observe(image));
        }
    });
})(document, window);