iframe lazy loading

Iframe lazy loading on scroll. Iframe_height to adapt on scroll loading

function iframeLazyLoading(iframe_height) {

	var iframes = $('iframe');

	$(document).on("scroll", function(event) {

		iframes.each(function(index) {
			var iframe = $(this);
			if ($(document).scrollTop() > index*iframe_height) {
				if (iframe.attr('src') === undefined || iframe.attr('src') === '') {

					iframe.attr('src', function() {
						return iframe.data('src');
					});

					iframe.attr('data-src', function() {
						var src = iframe.attr('src');
						iframe.removeAttr('data-src');
						return src;
					});
				}
			}
		});

	});

}