Storage polyfill

storage_polyfill.js

/*
  Storage Polyfill by Remy Sharp.
  Delinted by Samuel Cole.
*/

if (typeof window.localStorage === 'undefined' || typeof window.sessionStorage === 'undefined') {
  (function () {

    var Storage = function (type) {
      function createCookie(name, value, days) {
        var date, expires;

        if (days) {
          date = new Date();
          date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000));
          expires = "; expires=" + date.toGMTString();
        } else {
          expires = "";
        }
        document.cookie = name + "=" + value + expires + "; path=/";
      }

      function readCookie(name) {
        var nameEQ = name + "=",
          ca = document.cookie.split(';'),
          i, 
          c;

        for (i = 0; i < ca.length; i += 1) {
          c = ca[i];
          while (c.charAt(0) === ' ') {
            c = c.substring(1, c.length);
          }

          if (c.indexOf(nameEQ) === 0) {
            return c.substring(nameEQ.length, c.length);
          }
        }
        return null;
      }
      
      function setData(data) {
        data = JSON.stringify(data);
        if (type === 'session') {
          window.name = data;
        } else {
          createCookie('localStorage', data, 365);
        }
      }
      
      function clearData() {
        if (type === 'session') {
          window.name = '';
        } else {
          createCookie('localStorage', '', 365);
        }
      }
      
      function getData() {
        var data = type === 'session' ? window.name : readCookie('localStorage');
        return data ? JSON.parse(data) : {};
      }


      // initialise if there's already data
      var data = getData();

      return {
        length: 0,
        clear: function () {
          data = {};
          this.length = 0;
          clearData();
        },
        getItem: function (key) {
          return data[key] === undefined ? null : data[key];
        },
        key: function (i) {
          // not perfect, but works
          var ctr = 0, k;
          for (k in data) {
            if (ctr === i) {
              return k;
            } else {
              ctr += 1;
            }
          }
          return null;
        },
        removeItem: function (key) {
          delete data[key];
          this.length -= 1;
          setData(data);
        },
        setItem: function (key, value) {
          data[key] = value.toString(); // forces the value to a string
          this.length += 1;
          setData(data);
        }
      };
    };

    if (typeof window.localStorage === 'undefined') {
      window.localStorage = new Storage('local');
    }
    if (typeof window.sessionStorage === 'undefined') {
      window.sessionStorage = new Storage('session');
    }

  }());
}