option-2.js

let pouchMiddleware
let invalidate = true;

const MyWrapperMiddleware = store => next => action => {
  const state = store.getState()

  if (!state.isLoggedIn)
    return next(action)

  if (someConditionForChange) {
    invalidate = true
    /* clean up, kill listeners if needed */
  }

  if (!invalidate) {
    invalidate = false
    pouchMiddleware = PouchMiddleware({
      path: state.currentPath,
      db,
      actions: {
        remove: doc => { return { type: types.DELETE_TODO, id: doc._id } },
        insert: doc => { return { type: types.INSERT_TODO, todo: doc } },
        batchInsert: docs => { return { type: types.BATCH_INSERT_TODOS, todos: docs } }
        update: doc => { return { type: types.UPDATE_TODO, todo: doc } },
      }
    })
  }

  return pouchMiddleware(store)(next)(action)
}

export default MyWrapperMiddleware;