Function duplicate

test/specs/with-handler.js:17–31

(emitter, event)

  const emitEventMirror = (emitter, event) => emitter.emitEvent(event)

  const duplicate = (emitter, event) => {
    if (event.type === 'value') {
      emitter.emit(event.value)
      if (!event.current) {
        return emitter.emit(event.value)
      }
    } else if (event.type === 'error') {
      emitter.error(event.value)
      if (!event.current) {
        return emitter.error(event.value)
      }
    } else {
      return emitter.end()
    }
  }

  describe('stream', () => {
    it('should return stream', () => {