Lazyloading

lazyloading.md

document.addEventListener("DOMContentLoaded", function() {
  var lazyloadImages;    

  if ("IntersectionObserver" in window) {
    lazyloadImages = document.querySelectorAll(".lazy");
    var imageObserver = new IntersectionObserver(function(entries, observer) {
      entries.forEach(function(entry) {
        if (entry.isIntersecting) {
          var image = entry.target;
          image.src = image.dataset.src;
          image.classList.remove("lazy");
          imageObserver.unobserve(image);
        }
      });
    });

    lazyloadImages.forEach(function(image) {
      imageObserver.observe(image);
    });
  } else {  
    var lazyloadThrottleTimeout;
    lazyloadImages = document.querySelectorAll(".lazy");
    
    function lazyload () {
      if(lazyloadThrottleTimeout) {
        clearTimeout(lazyloadThrottleTimeout);
      }    

      lazyloadThrottleTimeout = setTimeout(function() {
        var scrollTop = window.pageYOffset;
        $.each(lazyloadImages, function(i, img){
          if(img.offsetTop < (window.innerHeight + scrollTop)) {
                img.src = img.dataset.src;
                img.classList.remove('lazy');
          }
        });
       
        if(lazyloadImages.length == 0) { 
          document.removeEventListener("scroll", lazyload);
          window.removeEventListener("resize", lazyload);
          window.removeEventListener("orientationChange", lazyload);
        }
      }, 20);
    }

    document.addEventListener("scroll", lazyload);
    window.addEventListener("resize", lazyload);
    window.addEventListener("orientationChange", lazyload);
  }
});
document.addEventListener("DOMContentLoaded", function() {
  var lazyloadImages;    

  if ("IntersectionObserver" in window) {
    lazyloadImages = document.querySelectorAll(".lazybg");
    var imageObserver = new IntersectionObserver(function(entries, observer) {
      entries.forEach(function(entry) {
        if (entry.isIntersecting) {
          var image = entry.target;
          image.classList.remove("lazybg");
          imageObserver.unobserve(image);
        }
      });
    });

    lazyloadImages.forEach(function(image) {
      imageObserver.observe(image);
    });
  } else {  
    var lazyloadThrottleTimeout;
    lazyloadImages = document.querySelectorAll(".lazybg");
    
    function lazyload () {
      if(lazyloadThrottleTimeout) {
        clearTimeout(lazyloadThrottleTimeout);
      }    

      lazyloadThrottleTimeout = setTimeout(function() {
        var scrollTop = window.pageYOffset;
 
        $.each(lazyloadImages, function(i, img){
          if(img.offsetTop < (window.innerHeight + scrollTop)) {
                img.src = img.dataset.src;
                img.classList.remove('lazybg');
          }
        });
        if(lazyloadImages.length == 0) { 
          document.removeEventListener("scroll", lazyload);
          window.removeEventListener("resize", lazyload);
          window.removeEventListener("orientationChange", lazyload);
        }
      }, 20);
    }

    document.addEventListener("scroll", lazyload);
    window.addEventListener("resize", lazyload);
    window.addEventListener("orientationChange", lazyload);
  }
})

background lazy loading

<a data-aos="zoom-out" data-aos-delay="0" href="https://www.markzproperties.com/guaranteed-sold-program?hsLang=en" class="lazybg" style="background-image:url('https://www.markzproperties.com/hubfs/Guaranteed-Sold-1.png')">
            <span><div id="hs_cos_wrapper_module_154089726840750_" class="hs_cos_wrapper hs_cos_wrapper_widget hs_cos_wrapper_type_inline_text" style="" data-hs-cos-general-type="widget" data-hs-cos-type="inline_text" data-hs-cos-field="area_heading">Guaranteed Sale Program</div>
            </span>
            
          </a>

image lazy loading

<img data-aos-anchor=".fans-slider" data-aos-delay="400" data-aos="flip-down" class="person-image lazy" data-src="https://cdn2.hubspot.net/hubfs/4566933/No-Image.png" alt="Jessica Winekoff" width="96" height="96">