Example redux middleware

persist-to-ls-redux-middleware.js

import { STAR_PERSON, MET_PERSON, UPDATE_NOTES, SET_URL } from '../constants/action-types'
import { LS_KEY } from '../constants/localstorage-keys'
import tryit from 'tryit'
import debounce from 'lodash.debounce'

const userPreferenceActions = [STAR_PERSON, MET_PERSON, UPDATE_NOTES]

function writeToLocalStorage (getState) {
  let data = {
    starred: {},
    met: {},
    notes: {}
  }
  getState().personData.originalPersons.forEach(person => {
    if (person.notes) data.notes[person.slug] = person.notes
    if (person.starred) data.starred[person.slug] = true
    if (person.met) data.met[person.slug] = true
  })
  window.localStorage[LS_KEY] = JSON.stringify(data)
}

const debouncedWrite = debounce(writeToLocalStorage, 300)

export default function persistMiddleware (getState) {
  return next =>
    action => {
      next(action)
      // write person data changes to localStorage
      if (action && userPreferenceActions.indexOf(action.type) !== -1) {
        debouncedWrite(getState)
      }

      // write last url to localStorage
      if (action.type === SET_URL) {
        window.localStorage.lastUrl = action.text
      }
    }
}