Angular LocalStorage Key Value Store

user-prefs-service.coffee

angular.factory 'userPrefsService', (localStorageService) ->
  STORAGE_KEY = 'userPrefs'
  userPrefs = localStorageService.get(STORAGE_KEY) || {}
  return {
    set: (key, obj) ->
      if !key? || key.length == 0
        throw new Error('A key is required to store a value in the store')

      if obj == null
        delete userPrefs[key]
      else
        userPrefs[key] = obj

      localStorageService.set(STORAGE_KEY, angular.toJson(userPrefs))
    get: (key) ->
      if !key? || key.length == 0
        throw new Error('A key is required to retrieve a value from the store')

      if !localStorageService.get(STORAGE_KEY)?
        return null
      
      return angular.fromJson(localStorageService.get(STORAGE_KEY))[key]
  }

user-prefs-service_spec.coffee

describe 'user preferences service', ->

  userPrefsService = null
  beforeEach(module('LocalStorageModule'))

  beforeEach(inject( (_userPrefsService_) ->
    userPrefsService = _userPrefsService_
  ))

  it 'should store and retrieve a string value by key', ->
    userPrefsService.set('hobby', 'tennis')
    storedVal = userPrefsService.get('hobby')
    expect(storedVal).toEqual('tennis')

  it 'should append new properties by key', ->
    userPrefsService.set('hobby', 'tennis')
    userPrefsService.set('job', 'cook')
    storedValHobby = userPrefsService.get('hobby')
    storedValJob = userPrefsService.get('job')
    expect(storedValHobby).toEqual('tennis')
    expect(storedValJob).toEqual('cook')

  it 'should store and retrieve an array by key', ->
    userPrefsService.set('beatles', [{ id: 1, name: 'John' }, { id: 2, name: 'Paul' }])
    storedVal = userPrefsService.get('beatles')
    expect(storedVal[1].id).toEqual(2)
    expect(storedVal[0].name).toEqual('John')

  it 'should store and retrieve an array by key', ->
    storedVal = userPrefsService.get('ramones')
    expect(storedVal).not.toBeDefined()

  it 'should update an existing value', ->
    userPrefsService.set('hobby', 'tennis')
    userPrefsService.set('hobby', 'soccer')
    storedVal = userPrefsService.get('hobby')
    expect(storedVal).toEqual('soccer')

  it 'should throw an error when trying to retrieve a value without key', ->
    expect(-> userPrefsService.get()).toThrow(new Error('A key is required to retrieve a value from the store'))

  it 'should throw an error when trying to store a value without key', ->
    expect(-> userPrefsService.set()).toThrow(new Error('A key is required to store a value in the store'))

  it 'should be able to remove a key', ->
    userPrefsService.set('hobby', 'tennis')
    userPrefsService.set('hobby', null)
    storedVal = userPrefsService.get('hobby')
    expect(storedVal).toBeUndefined()