Lazy load script

gistfile1.txt

var allImages = document.querySelectorAll('img'), imageIndex;
for (imageIndex = 0; imageIndex < allImages.length; ++imageIndex) {
  var src = allImages[imageIndex].getAttribute('src');
  allImages[imageIndex].removeAttribute('src');
  allImages[imageIndex].setAttribute('data-src',src);
}

var allIframes = document.querySelectorAll('iframe'), iframeIndex;
for (iframeIndex = 0; iframeIndex < allIframes.length; ++iframeIndex) {
  var src = allIframes[iframeIndex].getAttribute('src');
  allIframes[iframeIndex].removeAttribute('src');
  allIframes[iframeIndex].setAttribute('data-src',src);
}

var allBgImages = document.querySelectorAll('[style*=background-image]'), imageBgIndex;
for (imageBgIndex = 0; imageBgIndex < allBgImages.length; ++imageBgIndex) {
  var url = allBgImages[imageBgIndex].style.backgroundImage;
  allBgImages[imageBgIndex].style.backgroundImage = '';
  allBgImages[imageBgIndex].setAttribute('data-bg',url);
}

window.lazyLoadOptions = {
  elements_selector: "img, [data-bg], iframe"
};

//lazy load plugin
function _extends(){return(_extends=Object.assign||function(t){for(var e=1;e<arguments.length;e++){var n=arguments[e];for(var o in n)Object.prototype.hasOwnProperty.call(n,o)&&(t[o]=n[o])}return t}).apply(this,arguments)}function _typeof(t){return(_typeof="function"==typeof Symbol&&"symbol"==typeof Symbol.iterator?function(t){return typeof t}:function(t){return t&&"function"==typeof Symbol&&t.constructor===Symbol&&t!==Symbol.prototype?"symbol":typeof t})(t)}!function(t,e){"object"===("undefined"==typeof exports?"undefined":_typeof(exports))&&"undefined"!=typeof module?module.exports=e():"function"==typeof define&&define.amd?define(e):t.LazyLoad=e()}(this,function(){"use strict";var t="undefined"!=typeof window,e=t&&!("onscroll"in window)||"undefined"!=typeof navigator&&/(gle|ing|ro)bot|crawl|spider/i.test(navigator.userAgent),n=t&&"IntersectionObserver"in window,o=t&&"classList"in document.createElement("p"),r={elements_selector:"img",container:e||t?document:null,threshold:300,thresholds:null,data_src:"src",data_srcset:"srcset",data_sizes:"sizes",data_bg:"bg",class_loading:"loading",class_loaded:"loaded",class_error:"error",load_delay:0,auto_unobserve:!0,callback_enter:null,callback_exit:null,callback_reveal:null,callback_loaded:null,callback_error:null,callback_finish:null},a=function(t,e){return t.getAttribute("data-"+e)},s=function(t,e,n){var o="data-"+e;null!==n?t.setAttribute(o,n):t.removeAttribute(o)},i=function(t){return"true"===a(t,"was-processed")},c=function(t,e){return s(t,"ll-timeout",e)},l=function(t){return a(t,"ll-timeout")},u=function(t,e){var n,o=new t(e);try{n=new CustomEvent("LazyLoad::Initialized",{detail:{instance:o}})}catch(t){(n=document.createEvent("CustomEvent")).initCustomEvent("LazyLoad::Initialized",!1,!1,{instance:o})}window.dispatchEvent(n)};var d=function(t,e){t&&t(e)},f=function(t,e){t._loadingCount+=e,0===t._elements.length&&0===t._loadingCount&&d(t._settings.callback_finish)},_=function(t){for(var e,n=[],o=0;e=t.children[o];o+=1)"SOURCE"===e.tagName&&n.push(e);return n},v=function(t,e,n){n&&t.setAttribute(e,n)},g=function(t,e){v(t,"sizes",a(t,e.data_sizes)),v(t,"srcset",a(t,e.data_srcset)),v(t,"src",a(t,e.data_src))},b={IMG:function(t,e){var n=t.parentNode;n&&"PICTURE"===n.tagName&&_(n).forEach(function(t){g(t,e)});g(t,e)},IFRAME:function(t,e){v(t,"src",a(t,e.data_src))},VIDEO:function(t,e){_(t).forEach(function(t){v(t,"src",a(t,e.data_src))}),v(t,"src",a(t,e.data_src)),t.load()}},m=function(t,e){var n,o,r=e._settings,s=t.tagName,i=b[s];if(i)return i(t,r),f(e,1),void(e._elements=(n=e._elements,o=t,n.filter(function(t){return t!==o})));!function(t,e){var n=a(t,e.data_src),o=a(t,e.data_bg);n&&(t.style.backgroundImage='url("'.concat(n,'")')),o&&(t.style.backgroundImage=o)}(t,r)},h=function(t,e){o?t.classList.add(e):t.className+=(t.className?" ":"")+e},p=function(t,e,n){t.addEventListener(e,n)},y=function(t,e,n){t.removeEventListener(e,n)},E=function(t,e,n){y(t,"load",e),y(t,"loadeddata",e),y(t,"error",n)},w=function(t,e,n){var r=n._settings,a=e?r.class_loaded:r.class_error,s=e?r.callback_loaded:r.callback_error,i=t.target;!function(t,e){o?t.classList.remove(e):t.className=t.className.replace(new RegExp("(^|\\s+)"+e+"(\\s+|$)")," ").replace(/^\s+/,"").replace(/\s+$/,"")}(i,r.class_loading),h(i,a),d(s,i),f(n,-1)},k=function(t,e){var n=function n(r){w(r,!0,e),E(t,n,o)},o=function o(r){w(r,!1,e),E(t,n,o)};!function(t,e,n){p(t,"load",e),p(t,"loadeddata",e),p(t,"error",n)}(t,n,o)},I=["IMG","IFRAME","VIDEO"],L=function(t,e){var n=e._observer;z(t,e),n&&e._settings.auto_unobserve&&n.unobserve(t)},x=function(t){var e=l(t);e&&(clearTimeout(e),c(t,null))},A=function(t,e){var n=e._settings.load_delay,o=l(t);o||(o=setTimeout(function(){L(t,e),x(t)},n),c(t,o))},z=function(t,e,n){var o=e._settings;!n&&i(t)||(I.indexOf(t.tagName)>-1&&(k(t,e),h(t,o.class_loading)),m(t,e),function(t){s(t,"was-processed","true")}(t),d(o.callback_reveal,t))},O=function(t){return!!n&&(t._observer=new IntersectionObserver(function(e){e.forEach(function(e){return function(t){return t.isIntersecting||t.intersectionRatio>0}(e)?function(t,e){var n=e._settings;d(n.callback_enter,t),n.load_delay?A(t,e):L(t,e)}(e.target,t):function(t,e){var n=e._settings;d(n.callback_exit,t),n.load_delay&&x(t)}(e.target,t)})},{root:(e=t._settings).container===document?null:e.container,rootMargin:e.thresholds||e.threshold+"px"}),!0);var e},N=function(t,e){this._settings=function(t){return _extends({},r,t)}(t),this._loadingCount=0,O(this),this.update(e)};return N.prototype={update:function(t){var n=this,o=this._settings,r=t||o.container.querySelectorAll(o.elements_selector);this._elements=function(t){return t.filter(function(t){return!i(t)})}(Array.prototype.slice.call(r)),!e&&this._observer?this._elements.forEach(function(t){n._observer.observe(t)}):this.loadAll()},destroy:function(){var t=this;this._observer&&(this._elements.forEach(function(e){t._observer.unobserve(e)}),this._observer=null),this._elements=null,this._settings=null},load:function(t,e){z(t,this,e)},loadAll:function(){var t=this;this._elements.forEach(function(e){L(e,t)})}},t&&function(t,e){if(e)if(e.length)for(var n,o=0;n=e[o];o+=1)u(t,n);else u(t,e)}(N,window.lazyLoadOptions),N});