Simple localStorage polyfill, based on https://gist.github.com/juliocesar/926500.

localStoragePolyfill.js

(function () {
  function isSupported() {
    try {
        return 'localStorage' in window && window['localStorage'] !== null;
    } catch(e) {
        return false;
    }
  }

  if (!isSupported()) {
    function init(undef) {
      var store = {
        setItem: function (id, val) {
          return store[id] = String(val);
        },
        getItem: function (id) {
          return store.hasOwnProperty(id) ? String(store[id]) : undef;
        },
        removeItem: function (id) {
          return delete store[id];
        },
        clear: function () {
          init();
        }
      };

      window.localStorage = store;
    }
    init();
  }
}());