This is the best localStorage polyfill in the world

best-localStorage-polyfill-evar.js

// I mean, seriously, localStorage is supported even by your mum. How about instead of
// casing the feature out, you give users in-memory (stale) storage instead?
// If they close your application, they deserve to lose data anyway.

if (!('localStorage' in window)) {
  window.localStorage = {
    _data       : {},
    setItem     : function(id, val) { return this._data[id] = String(val); },
    getItem     : function(id) { return this._data.hasOwnProperty(id) ? this._data[id] : null; },
    removeItem  : function(id) { return delete this._data[id]; },
    clear       : function() { return this._data = {}; }
  };
}