scravizo lets you configure and reconfigure your webpage, in real-time, from your server.
it has an API for sending data to the web client, for changing the layout of your client, for receiving data from the user, and for instantiating components in the client. "components" consist of other javascript projects within divs, which you can place anywhere on the screen on one of any number of pages that you provide to the user.
There's an example, with no server, here. Next I'll put up a sample application, with a server side.