text: import Subscriber from '../Subscriber';
  export default function defaultIfEmpty(defaultValue = null) {
      return this.lift(new DefaultIfEmptyOperator(defaultValue));
  }
  class DefaultIfEmptyOperator {
      constructor(defaultValue) {
          this.defaultValue = defaultValue;
      }
      call(subscriber) {
          return new DefaultIfEmptySubscriber(subscriber, this.defaultValue);
      }
  }
  class DefaultIfEmptySubscriber extends Subscriber {
      constructor(destination, defaultValue) {
          super(destination);
          this.defaultValue = defaultValue;
          this.isEmpty = true;
      }
      _next(x) {
          this.isEmpty = false;
          this.destination.next(x);
      }
      _complete() {
          if (this.isEmpty) {
              this.destination.next(this.defaultValue);
          }
          this.destination.complete();
      }
  }
  