code: function(type, envelope, complete) {
              // We send the message by navigating the browser to a special URL.
              // The iOS library will catch the navigation, prevent the UIWebView
              // from continuing, and use the data in the URL to execute code
              // within the iOS app.
  
              var dispatcher = this;
  
              this.callbacks[envelope.id] = function() {
                  complete();
  
                  delete dispatcher.callbacks[envelope.id];
              };
  
  	    var src = "jockey://" + type + "/" + envelope.id + "?" + encodeURIComponent(JSON.stringify(envelope));
              var iframe = document.createElement("iframe"); 
              iframe.setAttribute("src", src); 
              document.documentElement.appendChild(iframe); 
              iframe.parentNode.removeChild(iframe); 
              iframe = null; 
  	  }
docs: `type` can either be "event" or "callback"