ls.custommedia.js

/*
 html:after {
 	display: none;
 	content: '--small: (max-width: 500px) | --medium: (max-width: 1100px) | --large: (min-width: 1100px)';
 }
*/
(function(window){
	/*jshint eqnull:true */
	'use strict';
	var docElem = document.documentElement;

	var create = function(){
		if(!window.lazySizes || window.lazySizes.getCustomMedias){return;}
		var lazySizes = window.lazySizes;

		lazySizes.getCustomMedias = (function(){
			var regCleanPseudos = /['"]/g;
			var regSplit = /\s*\|\s*/g;
			var regNamedQueries = /^([a-z0-9_-]+)\s*:\s*(.+)$/i;

			var getStyle = function(elem, pseudo){
				return ((getComputedStyle(elem, pseudo) || {getPropertyValue: function(){}}).getPropertyValue('content') || 'none').replace(regCleanPseudos, '').trim();
			};
			var parse = function(string, object){
				string.split(regSplit).forEach(function(query){
					if(query.match(regNamedQueries)){
						object[RegExp.$1] = RegExp.$2;
					}
				});
			};
			return function(object, element){
				object = object || lazySizes.cfg.customMedia;
				element = element || document.querySelector('html');
				parse(getStyle(element, ':before'), object);
				parse(getStyle(element, ':after'), object);
				return object;
			};
		})();

		lazySizes.updateCustomMedia = function(){
			var i, len, customMedia;
			var elems = docElem.querySelectorAll('source[media][data-media][srcset]');

			lazySizes.getCustomMedias();

			for(i = 0, len = elems.length; i < len; i++){
				if( (customMedia = lazySizes.cfg.customMedia[elems[i].getAttribute('data-media') || elems[i].getAttribute('media')]) ){
					elems[i].setAttribute('media', customMedia);
				}
			}

			elems = docElem.querySelector('source[media][data-media][srcset] ~ img');
			for(i = 0, len = elems.length; i < len; i++){
				lazySizes.uP(elems[i]);
			}

			lazySizes.autoSizer.checkElems();
		};

		lazySizes.getCustomMedias();
		docElem.removeEventListener('lazybeforeunveil', create);
	};

	if(window.addEventListener){
		docElem.addEventListener('lazybeforeunveil', create);
		create();
		setTimeout(create);
	}

})(window);