function loadImages(block) {
  Array.from(block.querySelectorAll('img[data-src]')).forEach(function (img, i) {
    let _img = new Image,
        _src = img.getAttribute('data-src');
    let wrap = img.closest('.is-loader');
    _img.onload = function () {
      img.src = _src;
      img.classList.add('is-loaded');
      if (wrap.length > 0) wrap.classList.remove('is-loader');
    }
    if (img.src !== _src) _img.src = _src;
  });
}

document.addEventListener("DOMContentLoaded", function (event) {
    setTimeout(function() {
        document.querySelectorAll('*').forEach.call(
            document.querySelectorAll('img[data-src]'),
            function (img) {
                img.setAttribute('src', img.getAttribute('data-src'));
                img.onload = function () {
                    img.removeAttribute('data-src');
                };
            });
    },200);
});