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(function($) {
function parseImagesFromCSS(doc) {
var i, j,
rule,
image,
pattern = /url\((.*)\)/,
properties = ['background-image', '-webkit-border-image'],
images = {};
if (doc.styleSheets) {
for (i = 0; i < doc.styleSheets.length; ++i) {
images = $.extend(images, parseImagesFromCSS(doc.styleSheets[i]));
}
} else if (doc.cssRules) {
for (i = 0; i < doc.cssRules.length; ++i) {
rule = doc.cssRules[i];
if (rule.styleSheet) {
images = $.extend(images, parseImagesFromCSS(rule.styleSheet));
} else if (rule.style) {
for (j=0; j < properties.length; j++) {
image = pattern.exec(rule.style.getPropertyValue(properties[j]));
if (image && image.length === 2) {
images[image[1]] = image[0];
}
}
}
}
}
return images;
};
$.extend({
preload: {
images: function(doc) {
doc = doc || document;
var images = $.map(parseImagesFromCSS(doc), function(url) { return url; }),
head = doc.getElementsByTagName('head')[0],
style = doc.createElement('style');
style.type = 'text/css';
style.id = 'preload';
style.innerHTML = 'body::after { content: ' + images.join(' ') + '; display: none; }';
head.appendChild(style);
}
}
});
})(jQuery);
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