JavaScript web apps are fine, as long as they are "isomorphic", i.e. the front-end code is also run on the server and the resulting HTML is sent to the client,

JavaScript web apps are fine, as long as they are "isomorphic", i.e. the front-end code is also run on the server and the resulting HTML is sent to the client, and as long as it's possible to at least navigate to and read all the content without having JavaScript enabled.