For years I developed web applications with frameworks like JSP, Struts, JSF, PHP or ASP.NET. And all these frameworks are generating HTML code on the server.
When we look at Java EE or other server side frameworks we will find the perfect server interface for such applications: REST with JSON. So there is no need to do any conversion on the client side.
When I was think about my ideas and developing a sample application one of my colleagues pointed me on ROCA. And I completely agree with all recommendations! So have a look: http://roca-style.org/