storage.js

if (typeof window.localStorage == 'undefined' || typeof window.sessionStorage == 'undefined') (function () {
// Define the storage type (local or session)
var Storage = function (type) {
  // Define the storage type (local or session)
  function setData(data) {
    // Sets the data into storage
  }
  function clearData() {
    // clears data from storage
  }
  return {
    length: 0,
    clear: function () {
      clearData();
    },
    getItem: function (key) {
      return data[key] === undefined ? null : data[key];
    },
    key: function (i) {
      var ctr = 0;
      for (var k in data) {
        if (ctr == i) return k;
        else ctr++;
      }
      return null;
    },
    removeItem: function (key) {
      delete data[key];
      this.length--;
      setData(data);
    },
    setItem: function (key, value) {
      data[key] = value + '';
      this.length++;
      setData(data);
    }
  };
};
// Set the local and session storage properties inside the window 
// object
if (typeof window.localStorage == 'undefined') window.localStorage = new Storage('local');
if (typeof window.sessionStorage == 'undefined') window.sessionStorage = new Storage('session');
})();