; (function () {
    const ob = new IntersectionObserver((entries) => {
        entries.filter(entry => entry.isIntersecting).forEach(entry => {
            const img = entry.target;
            img.src = img.dataset.src;
            ob.unobserve(img);
        })
    })

    const imgs = document.querySelectorAll('img[data-src]');
    imgs.forEach(img => { ob.observe(img) });
})();