local_storage_cache.js

(function (root, module) {
  'use strict';
  
  if (!module) {
    module = root;
  }
  
  var _keys = Object.keys || function (o) {
    var keys = [];
    for (var prop in o) {
      if (o.hasOwnProperty(prop)) {
        keys.push(prop);
      }
    }
    return keys;
  };
  
  var _toString = Object.prototype.toString;
  var _type = function (x) {
    return _toString.call(x);
  };
  
  /**
   * @class Cache
   *
   * @param {Storage} storage An object implementing the Storage interface
   * http://www.w3.org/TR/webstorage/#the-storage-interface
   */
  function Cache(storage, options) {
    this.options = options || {};
    this.storage = storage;
    this._length();
  }
  module.Cache = Cache;
  
  Cache.localStorage = function (Fake) {
    var storage;
    try {
      storage = window.localStorage;
    } catch (e) {};
    if (!storage) {
      storage = new (Fake || Cache.LocalStorageCompat)();
    }
    return new Cache(storage);
  };
  
  Cache.prototype._getFullItem = function (key) {
    var item = this.storage.getItem(key);
    if (item) {
      item = JSON.parse(item);
    } else {
      item = {value: null, expire: null};
    }
    if (_type(item) !== '[object Object]' || !('value' in item && 'expire' in item)) {
      throw new Error('Can\'t get "' + key + '": invalid format');
    }
    return item;
  };
  
  /**
   * @param {String} key The key to find the value for
   *
   * @return {*} The JSON-parsed value
   */
  Cache.prototype.getItem = Cache.prototype.get = function (key) {
    return this._getFullItem(key).value;
  };
  
  /**
   * @param {String} key The key to save the value under
   * @param {Object} value The JSON-encodable value to store
   * @param {Date|Number} expire The date when this key should expire or the number of seconds from now this key should expire
   */
  Cache.prototype.setItem = Cache.prototype.set = function (key, value, expire) {
    var expireDate;
    if (expire) {
      if (expire.getTime) {
        expireDate = expire.getTime();
      } else if (typeof expire === 'number') {
        expireDate = new Date().getTime() + (expire * 1000);
      } else {
        throw new Error('expire must be either a Date or a Number');
      }
    } else {
      throw new Error('options.expire is a required option');
    }
    try {
      this.storage.setItem(key, JSON.stringify({
        expire: expireDate,
        value: value
      }));
      this._length();
    } catch (e) {
      if (e === 'QUOTA_EXCEEDED_ERR') {
        this.purge();
        // Retry after the purge.
        this.setItem.apply(this, arguments);
      } else {
        throw e;
      }
    }
  };
  
  Cache.prototype.removeItem = Cache.prototype.remove = function (key) {
    this.storage.removeItem(key);
    this._length();
  };
  
  Cache.prototype.clear = function () {
    this.storage.clear();
    this.length = this.storage.length;
  };
  
  Cache.prototype.purge = function () {
    var now = new Date();
    for (var i = 0, len = this.length; i < len; i++) {
      var key = this.storage.key(i);
      var item = this._getFullItem(key);
      if (now > item.expire) {
        this.removeItem(key);
        if (this.options.conservativePurge) {
          return;
        }
      }
    }
  };
         
  Cache.prototype._length = function () {
    return this.length = this.storage.length;
  };
  
  
  Cache.LocalStorageCompat = (function () {
    function LocalStorageCompat() {
      this.clear();
    }
    
    LocalStorageCompat.prototype.setItem = function (key, value) {
      this.storage[key] = '' + value;
      this._keys();
    };
    
    LocalStorageCompat.prototype.getItem = function (key) {
      return '' + this.storage[key];
    };
    
    LocalStorageCompat.prototype.removeItem = function (key) {
      delete this.storage[key];
      this._keys();
    };
    
    LocalStorageCompat.prototype.clear = function () {
      this.storage = {};
      this._keys();
    };
    
    LocalStorageCompat.prototype.key = function (i) {
      return this.keys[i];
    };
    
    LocalStorageCompat.prototype._keys = function () {
      this.keys = _keys(this.storage);
      this.length = this.keys.length;
    };
    
    return LocalStorageCompat;
  })();
  
})(typeof window !== 'undefined' ? window : global, typeof exports !== 'undefined' ? exports : null);