Created
April 26, 2021 10:48
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| $(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); | |
| } | |
| }) |
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