> javascript processing? Actually Javascript engines are extremely fast, the UI in a web app isn't because web engines have to deal with a complex repaint mode

> javascript processing? Actually Javascript engines are extremely fast, the UI in a web app isn't because web engines have to deal with a complex repaint model. Resources can be loaded asynchronously, so it's not really a bottleneck. On the other hand repaints can absolutely be a serious bottleneck in webpage. Native UI use a much much more simple model, which makes repaints less expensive and allow a better FPS rate. That's why webpages shouldn't try to look like native apps on mobile.