Vanilla Lazy Load

lazyload.js

//source: https://www.merixstudio.com/blog/lazy-loading-pure-javascript/
function lazyLoadInit(){
				let lazyImages = [].slice.call(document.querySelectorAll("img.lazy"));
				let active = false;
				var treshold = 100;
				const lazyLoad = function() {
					if (active === false) {
						active = true;
						
						setTimeout(function() {
							lazyImages.forEach(function(lazyImage) {
								if ((lazyImage.getBoundingClientRect().top-treshold <= window.innerHeight && lazyImage.getBoundingClientRect().bottom+treshold >= 0)) {
									lazyImage.src = lazyImage.dataset.src;
									lazyImage.classList.remove("lazy");
									
									lazyImages = lazyImages.filter(function(image) {
										return image !== lazyImage;
									});
									
									if (lazyImages.length === 0) {
										document.removeEventListener("scroll", lazyLoad);
										window.removeEventListener("orientationchange", lazyLoad);
									}
								}
							});
							
							active = false;
						}, 200);
					}
				};
				
				document.addEventListener("scroll", lazyLoad);
				window.addEventListener("resize", lazyLoad);
				window.addEventListener("orientationchange", lazyLoad);	
				document.dispatchEvent(new CustomEvent('scroll'))
			}
			AddOnLoadEvent(lazyLoadInit);

/*
//ADD TO ON LOAD EVENT
function AddOnLoadEvent(functionX) {
  var oldonloadevent = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = functionX;
  }
  else {
    window.onload = function () {
      if (oldonloadevent) {
        oldonloadevent();
      }
      functionX();
    }
  }
}
*/