code: function broadcast(event, data, destination) {
          if (!crosstab.supported) {
              notSupported();
          }
  
          var message = {
              id: util.generateId(),
              event: event,
              data: data,
              destination: destination,
              origin: crosstab.id,
              timestamp: util.now()
          };
  
          // If the destination differs from the origin send it out, otherwise
          // handle it locally
          if (message.destination !== message.origin) {
              setLocalStorageItem(util.keys.MESSAGE_KEY, message);
          }
  
          if (!message.destination || message.destination === message.origin) {
              eventHandler.emit(event, message);
          }
      }
docs: --- Setup message sending and handling ---