app.js

window.onload = function () {
    rclient = RClient.create({
        debug: false,
        host: (location.protocol == "https:") ? ("wss://"+location.hostname+":8083/") : ("ws://"+location.hostname+":8081/"),
        on_connect: function(ocaps) {
            rcloud = RCloud.create(ocaps.rcloud);
            if (rcloud.authenticated) {
                rcloud.session_init(rcloud.username(), rcloud.github_token(), function(hello) {
                    rclient.post_response(hello);
                });
            } else {
                rcloud.anonymous_session_init(function(hello) {
                    rclient.post_response(hello);
                });
            }
            rcloud.init_client_side_data();

            var extern=undefined;
            rcloud.get_ocaps('foo','ocaps', function(ocaps){
               if(ocaps.ok)
                    extern=ocaps.extern;
            });
            if(extern)
                extern.my_ocap(function(v) {console.log("hello"+v)});
            return true;
        }, on_error: function(msg, status_code) {
            // debugger;
            if (msg == 'Login failed. Shutting down!') {
                window.location =
                    (window.location.protocol +
                     '//' + window.location.host +
                     '/login.R?redirect=' +
                     encodeURIComponent(window.location.pathname + window.location.search));
                return true;
            } else
                return false;
        }
    });
}

ocaps.R

my.ocap <- function() {
  v <- "dolly"
}

ocaps <- function() {
  make.oc<-rcloud.support:::make.oc
   list(
      ok=TRUE,
      extern=list(
        my_ocap=make.oc(my_ocap)
      )
    )
}