+(function($) {
+ jQuery.fn.lazyload = function(pattern, options) {
+ var settings = {
+ threshold: 0,
+ scrollThreshold: 300,
+ placeholder: 'loading...',
+ checkInterval: 2000
+ };
+
+ if (options) {
+ $.extend(settings, options);
+ }
+
+ var container = this;
+ container.data('lastScroll', -10000);
+
+ function aboveViewport(container, element, threshold) {
+ return $(container).offset().top >= $(element).offset().top + $(element).height() + threshold;
+ }
+
+ function belowViewport(container, element, threshold) {
+ return $(container).offset().top + $(container).height() + threshold <= $(element).offset().top;
+ }
+
+ function checkScroll() {
+ if (Math.abs(container.scrollTop() - container.data('lastScroll')) > settings.scrollThreshold) {
+ container.data('lastScroll', container.scrollTop());
+
+ $(pattern, container).each(function() {
+ if (aboveViewport(container, this, settings.threshold)
+ || belowViewport(container, this, settings.threshold)) {
+ $(this).html(settings.placeholder);
+ } else {
+ $(this).html('<img src="' + $(this).attr('src') + '" width="' + $(this).width() + '" />');
+ }
+ })
+ }
+ setTimeout(checkScroll, settings.checkInterval);
+ }
+
+ checkScroll();
+ };
+})(jQuery);