Rx.Notification.prototype.kind
Gets the kind from the notification which denotes 'N' for OnNext, 'E' for OnError and 'C' for OnCompleted.
返回值
(String): The kind from the notification which denotes 'N' for OnNext, 'E' for OnError and 'C' for OnCompleted.
Example
var notification = Rx.Notification.createOnCompleted();
console.log(notification.kind);
// => C