How to make lazy loading of images?

How to make lazy loading of images?

<a data-fancybox="gallery" href="<?=CFile::GetPath($element[" preview_picture"])?>" class="gallery__item" style="background-image: url(<?=CFile::GetPath($element["PREVIEW_PICTURE"])?>)"></a>

I tried lazy loading not working - just does not display images. Maybe using AJAX ,but I have component bitrix.catalog.section.list