lazy background on jquery

$(document).ready(function () {
    var lazyloadBgImages = document.querySelectorAll(".lazybg");
    if ("IntersectionObserver" in window) {
        var bgImageObserver = new IntersectionObserver(function (entries, observer) {
            entries.forEach(function (entry) {
                if (entry.isIntersecting) {
                    var image = entry.target;
                    image.style["background-image"] = "url('" + image.dataset.bgsrc + "')";
                    image.classList.remove("lazybg");
                    bgImageObserver.unobserve(image);
                }
            });
        });

        lazyloadBgImages.forEach(function (image) {
            bgImageObserver.observe(image);
        });
    } else {
        var lazyloadThrottleTimeout;
        document.addEventListener("scroll", lazyload(lazyloadBgImages));
        window.addEventListener("resize", lazyload(lazyloadBgImages));
        window.addEventListener("orientationChange", lazyload(lazyloadBgImages));
    }


    var isIE11 = !!window.MSInputMethodContext && !!document.documentMode;
    console.log("ie11= " + isIE11);
    if (isIE11) {
        lazyloadBgImages.forEach(function (bgelement) {
                bgelement.style["background-image"] = "url('" + bgelement.dataset.bgsrc + "')";
                bgelement.classList.remove('lazybg');
        });
    }
    function lazyload(lazyloadBgImages) {
        if (lazyloadThrottleTimeout) {
            clearTimeout(lazyloadThrottleTimeout);
        }

        lazyloadThrottleTimeout = setTimeout(function () {
            
            var scrollTop = window.pageYOffset;
            lazyloadBgImages.forEach(function (bgelement) {
                if (bgelement.offsetTop < (window.innerHeight + scrollTop)) {
                    
                    bgelement.style["background-image"] = "url('" + bgelement.dataset.bgsrc + "')";
                    bgelement.classList.remove('lazybg');
                }
            });
            if (lazyloadBgImages.length === 0) {
                document.removeEventListener("scroll", lazyload);
                window.removeEventListener("resize", lazyload);
                window.removeEventListener("orientationChange", lazyload);
            }
        }, 20);
    }


})