Adam Roderick's version of CacheProvider with better packaging! http://jsperf.com/maher-cacheprovider

CacheProvider.js

(function (window, undefined) {
   
   /**
     * {Boolean} useLocalStorageIfAvailable - optional, defaults to true.  The CacheProvider object will 
     * use the HTML5 localStorage object, if available
     */
    var CacheProvider = (function() {
        
        var _hasLocalStorage,
            _useLocalStorage,
            _cache = [],
            CacheProviderOperations;
        
        try {
            _hasLocalStorage = (window.localStorage) && window.localStorage !== null;
        } catch (ex) {
            _hasLocalStorage = false;
        }
        
        if (_hasLocalStorage) {
            Storage.prototype.setObject = function(key, value) {
                this.setItem(key, JSON.stringify(value));
            };
        
            Storage.prototype.getObject = function(key) {
                return JSON.parse(this.getItem(key));
            };
        }
        
        CacheProviderOperations = {
    
            /**
             * {String} k - the key
             */
            get: function(k) {
                if (_useLocalStorage && _hasLocalStorage) {
                    var isObject = localStorage.getItem(k + '___isObject');
                    var action = isObject ? 'getObject' : 'getItem';
                    return localStorage[action](k) || undefined;
                } else {
                    return _cache[k] || undefined;
                }
            },
        
            /**
             * {String} k - the key
             * {Object} v - any kind of value you want to store
             */
            set: function(k, v) {
                if (_useLocalStorage && _hasLocalStorage) {
                    if (typeof v !== 'string') {
                        // make assumption if it's not a string, then we're storing an object
                        localStorage.setObject(k, v);                
                        localStorage.setItem(k + '___isObject', true);
                    } else {
                        try {
                            localStorage.setItem(k, v);
                        } catch (ex) {
                            if (ex.name == 'QUOTA_EXCEEDED_ERR') {
                                // developer needs to figure out what to start invalidating
                                throw new Exception(v);
                            }
                        }
                    }
                } else {
                    // put in our local object
                    _cache[k] = v;
                }
                // return our newly cached item
                return v;
            },
        
            /**
             * {String} k - the key
             * {Boolean} local - put this in local storage
             */
            clear: function(k) {
                if (_useLocalStorage && _hasLocalStorage) {
                    localStorage.removeItem(k);
                    localStorage.removeItem(k + '___isObject');
                }
                // delete in both caches - doesn't hurt.
                delete _cache[k];
            }
        };
            
        return function (useLocalStorageIfAvailable) {
            _useLocalStorage = 'undefined' == typeof(useLocalStorageIfAvailable) ? true : useLocalStorageIfAvailable;
            
            return CacheProviderOperations;
        };
        
    })();
           
    window.CacheProvider = CacheProvider;
})(this);

/*

Usage
------------------------------

var cache = new CacheProvider();

cache.set('maher', 'Maher Salam');

document.write('<p>' + cache.get('maher') + '</p>');

cache.clear('maher');

document.write('<p>' + cache.get('maher') + '</p>'); 

*/