parallax.js

function ParallaxItem(containerNode) {
	var container, bgElements, offset, bgHeight, containerHeight, maxScrolls, height;
	container = Y.one(containerNode);
	bgElements = container.all('.parallax-background');
	function refreshCoords() {
		offset = container.getY();
		containerHeight = container.get('offsetHeight');
		bgHeights = [];
		maxScrolls = [];
		bgElements.each(function(item) {
			height = item.get('offsetHeight');
			bgHeights.push(height);
			maxScrolls.push(containerHeight - height + 2);
		});
	}
	function refresh(docScrollY) {
		var i, j, scroll, transformParam;
		i = 0;
		bgElements.each(function(bgElement) {
			scroll = -Math.round(((docScrollY - offset) / containerHeight) * maxScrolls[i]);
			scroll = Math.max(scroll, maxScrolls[i]);
			var transformParam;
			if (!use2DTransform) {
				transformParam = 'translate3d(0px,' + scroll + 'px, 0px)';
			} else {
				transformParam = 'translateY(' + scroll + 'px)';
			}
			if (transform && transformParam) {
				bgElement.setStyle(transform, transformParam);
				bgElement.setStyle(prefixes.w3c, transformParam);
			} else {
				bgElement.setStyle('marginTop', scroll + 'px');
			}
			i++;
		});
	}
	refreshCoords();
	return {
		'refresh': refresh,
		'refreshCoords': refreshCoords
	}
}
function refreshParallaxItems() {
	var docScrollY = Y.DOM.docScrollY();
	if (!parallaxItems || !parallaxItems.length) {
		return false;
	}
	for (var i = 0, j = parallaxItems.length; i < j; i++) {
		parallaxItems[i].refresh(docScrollY);
	}
}
function scrollWatcher() {
	if (requestAnimationFrame) {
		requestAnimationFrame(refreshParallaxItems);
	} else {
		refreshParallaxItems();
	}
}
function addParallaxItem(containerNode) {
	parallaxItems.push(new ParallaxItem(containerNode));
	if (!scrollHandler) {
		scrollHandler = Y.on('scroll', scrollWatcher);
	}
}
if (useParallax) {
	nodes = Y.all('#flickr-frames .parallax-item');
	nodes.each(function(item) {
		addParallaxItem(item);
	});
	Y.on('PhotoListView:render', function() {
		var now = new Date();
		if (now - lastExec > 250) {
			for (var i = 0, j = parallaxItems.length; i < j; i++) {
				parallaxItems[i].refreshCoords();
			}
			lastExec = now;
		}
	});
	refreshParallaxItems();
}
}());