javascript cache

javascript_cache.js

//reference:http://www.dustindiaz.com/javascript-cache-provider
function CacheProvider() {
  // values will be stored here
  this._cache = {};
}

if (CacheProvider.hasLocalStorage) {
  Storage.prototype.setObject = function(key, value) {
    this.setItem(key, JSON.stringify(value));
  };


  Storage.prototype.getObject = function(key) {
    return JSON.parse(this.getItem(key));
  };
}

CacheProvider.prototype = {


  /**
     * {String} k - the key
     * {Boolean} local - get this from local storage?
     * {Boolean} o - is the value you put in local storage an object?
     */
  get: function(k, local, o) {
    if (local && CacheProvider.hasLocalStorage) {
      var action = o ? 'getObject' : 'getItem';
      return localStorage[action](k) || undefined;
    } else {
      return this._cache[k] || undefined;
    }
  },


  /**
     * {String} k - the key
     * {Object} v - any kind of value you want to store
     * however only objects and strings are allowed in local storage
     * {Boolean} local - put this in local storage
     */
  set: function(k, v, local) {
    if (local && CacheProvider.hasLocalStorage) {
      if (typeof v !== 'string') {
        // make assumption if it's not a string, then we're storing an object
        localStorage.setObject(k, v);
      } 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);
            return;
          }
        }
      }
    } else {
      // put in our local object
      this._cache[k] = v;
    }
    // return our newly cached item
    return v;
  },


  /**
     * {String} k - the key
     * {Boolean} local - put this in local storage
     * {Boolean} o - is this an object you want to put in local storage?
     */
  clear: function(k, local, o) {
    if (local && CacheProvider.hasLocalStorage) {
      localStorage.removeItem(k);
    }
    // delete in both caches - doesn't hurt.
    delete this._cache[k];
  }


};