mediawiki-skins-Citizen/resources/scripts/lazyload.js

/*
 * Citizen - Lazyload JS
 * https://starcitizen.tools
 *
 * Lazyloading images with Native API or IntersectionObserver
 */

// Native API
if ("loading" in HTMLImageElement.prototype) {
	document.querySelectorAll("img.lazy").forEach(function(img) {
		img.setAttribute("src", img.getAttribute("data-src"));
		if (img.hasAttribute("data-srcset")) {
			img.setAttribute("srcset", img.getAttribute("data-srcset"));
		}
		img.classList.remove("lazy");
	});
} else {
	// IntersectionObserver API
	if (typeof IntersectionObserver !== "undefined" && "forEach" in NodeList.prototype) {
		const observer = new IntersectionObserver(function (changes) {
			if ("connection" in navigator && navigator.connection.saveData === true) {
				return;
			}
			changes.forEach(function (change) {
				if (change.isIntersecting) {
					change.target.setAttribute("src", change.target.getAttribute("data-src"));
					if (change.target.hasAttribute("data-srcset")) {
						change.target.setAttribute("srcset", change.target.getAttribute("data-srcset"));
					}
					change.target.classList.remove("lazy");
					observer.unobserve(change.target);
				}
			});
		});
		document.querySelectorAll("img.lazy").forEach(function(img) {
			observer.observe(img);
		});
	}
}