Ember service:local-storage trivial wrapper for window.localStorage

local-storage-service-test.js

import { moduleFor } from 'ember-qunit'
import test from 'dummy/tests/ember-sinon-qunit/test'

moduleFor('service:local-storage')

const mockStore = { setItem() { }, removeItem() { } }

test('when localStorage throws an exception', function testCatch(assert) {
  const service = this.subject()
  const stub = this.stub(mockStore, 'setItem').throws()
  service.localStorage = mockStore
  service.length()
  assert.ok(stub.called, 'the exception is caught')
})

test('when localStorage is used', function testStorage(assert) {
  const service = this.subject()
  service.removeItem('foo') // ensure setting 'foo' increases length
  const startLength = service.length()
  service.setItem('foo', 'bar')
  assert.equal(service.getItem('foo'), 'bar', 'setItem stores a value by key and getItem gets it')
  assert.equal(service.length(), startLength + 1, 'setting an item increases the length')
  assert.ok(service.key(0), 'items can be fetched by key index')
  service.removeItem('foo')
  assert.equal(service.length(), startLength, 'removing an item decreases the length')
})

local-storage-service.js

import Ember from 'ember'

/**
 * Wraps window.localStorage and adds convenience property isSupported.
 * https://developer.mozilla.org/en-US/docs/Web/API/Storage/LocalStorage
 */
export default Ember.Service.extend({

  init() {
    try {
      this.localStorage = window.localStorage // test hook
    } catch (e) {
      this.localStorage = null
    }
  },

  isSupported: Ember.computed(function isSupported() {
    const uid = new Date()
    try {
      this.localStorage.setItem(uid, uid)
      this.localStorage.removeItem(uid)
      return true
    } catch (e) {
      return false
    }
  }),

  getItem(...args) {
    return this.get('isSupported') && this.localStorage.getItem(...args)
  },

  key(...args) {
    return this.get('isSupported') && this.localStorage.key(...args)
  },

  length() {
    return this.get('isSupported') && this.localStorage.length
  },

  removeItem(...args) {
    return this.get('isSupported') && this.localStorage.removeItem(...args)
  },

  setItem(...args) {
    return this.get('isSupported') && this.localStorage.setItem(...args)
  },
})