web-storage.js

function encode (value) {
  if (Object.prototype.toString.call(value) === '[object Date]') {
    return '__q_date|' + value.toUTCString()
  }
  if (Object.prototype.toString.call(value) === '[object RegExp]') {
    return '__q_expr|' + value.source
  }
  if (typeof value === 'number') {
    return '__q_numb|' + value
  }
  if (typeof value === 'boolean') {
    return '__q_bool|' + (value ? '1' : '0')
  }
  if (typeof value === 'string') {
    return '__q_strn|' + value
  }
  if (typeof value === 'function') {
    return '__q_strn|' + value.toString()
  }
  if (value === Object(value)) {
    return '__q_objt|' + JSON.stringify(value)
  }

  // hmm, we don't know what to do with it,
  // so just return it as is
  return value
}

function decode (value) {
  let type, length, source

  length = value.length
  if (length < 10) {
    // then it wasn't encoded by us
    return value
  }

  type = value.substr(0, 8)
  source = value.substring(9)

  switch (type) {
    case '__q_date':
      return new Date(source)

    case '__q_expr':
      return new RegExp(source)

    case '__q_numb':
      return Number(source)

    case '__q_bool':
      return Boolean(source === '1')

    case '__q_strn':
      return '' + source

    case '__q_objt':
      return JSON.parse(source)

    default:
      // hmm, we reached here, we don't know the type,
      // then it means it wasn't encoded by us, so just
      // return whatever value it is
      return value
  }
}

function generateFunctions (fn) {
  return {
    local: fn('local'),
    session: fn('session')
  }
}

let
  hasStorageItem = generateFunctions(
    (type) => (key) => window[type + 'Storage'].getItem(key) !== null
  ),

  getStorageLength = generateFunctions(
    (type) => () => window[type + 'Storage'].length
  ),

  getStorageItem = generateFunctions((type) => {
    let
      hasFn = hasStorageItem[type],
      storage = window[type + 'Storage']

    return (key) => {
      if (hasFn(key)) {
        return decode(storage.getItem(key))
      }
      return null
    }
  }),

  getStorageAtIndex = generateFunctions((type) => {
    let
      lengthFn = getStorageLength[type],
      getItemFn = getStorageItem[type],
      storage = window[type + 'Storage']

    return (index) => {
      if (index < lengthFn()) {
        return getItemFn(storage.key(index))
      }
    }
  }),

  getAllStorageItems = generateFunctions((type) => {
    let
      lengthFn = getStorageLength[type],
      storage = window[type + 'Storage'],
      getItemFn = getStorageItem[type]

    return () => {
      let
        result = {},
        key,
        length = lengthFn()

      for (let i = 0; i < length; i++) {
        key = storage.key(i)
        result[key] = getItemFn(key)
      }

      return result
    }
  }),

  setStorageItem = generateFunctions((type) => {
    let storage = window[type + 'Storage']
    return (key, value) => { storage.setItem(key, encode(value)) }
  }),

  removeStorageItem = generateFunctions((type) => {
    let storage = window[type + 'Storage']
    return (key) => { storage.removeItem(key) }
  }),

  clearStorage = generateFunctions((type) => {
    let storage = window[type + 'Storage']
    return () => { storage.clear() }
  }),

  storageIsEmpty = generateFunctions((type) => {
    let getLengthFn = getStorageLength[type]
    return () => getLengthFn() === 0
  })

export var LocalStorage = {
  has: hasStorageItem.local,
  get: {
    length: getStorageLength.local,
    item: getStorageItem.local,
    index: getStorageAtIndex.local,
    all: getAllStorageItems.local
  },
  set: setStorageItem.local,
  remove: removeStorageItem.local,
  clear: clearStorage.local,
  isEmpty: storageIsEmpty.local
}

export var SessionStorage = { // eslint-disable-line one-var
  has: hasStorageItem.session,
  get: {
    length: getStorageLength.session,
    item: getStorageItem.session,
    index: getStorageAtIndex.session,
    all: getAllStorageItems.session
  },
  set: setStorageItem.session,
  remove: removeStorageItem.session,
  clear: clearStorage.session,
  isEmpty: storageIsEmpty.session
}