code: function createCmdButton(cmd, label, forceCheckbox, className) {
          var button;
          button = document.createElement('button');
          button.className = className || 'btn';
          button.innerHTML = label;
          button.onclick = function() {
              var cl;
              var clients, doLogic;
              cl = node.game.clientList;
              // Get selected clients.
              clients = cl.getSelectedClients();
              if (!clients || clients.length === 0) return;
              // If the room's logic client is selected, handle it specially.
              if (node.game.roomLogicId) {
                  doLogic = J.removeElement(cl.roomLogicId, clients);
              }
  
              node.socket.send(node.msg.create({
                  target: 'SERVERCOMMAND',
                  text:   'ROOMCOMMAND',
                  data: {
                      type:    cmd,
                      roomId:  cl.roomId,
                      doLogic: !!doLogic,
                      clients: clients,
                      force:   forceCheckbox.checked
                  }
              }));
          };
  
          return button;
      }
docs: Helper functions. 
  Make a button that sends a given ROOMCOMMAND.