local_storage.js

(function (window) {
    var keyPrefix = '';
    var noPrefix = false;
    var cache = {};
    var useCs = false;
    var useLs = !useCs && !!window.localStorage;
    function storageSetPrefix(newPrefix) {
      keyPrefix = newPrefix;
    }
    function storageSetNoPrefix() {
      noPrefix = true;
    }
    function storageGetPrefix() {
      if (noPrefix) {
        noPrefix = false;
        return '';
      }
      return keyPrefix;
    }
    function storageGetValue() {
      var keys = Array.prototype.slice.call(arguments),
              callback = keys.pop(),
              result = [],
              single = keys.length == 1,
              value,
              allFound = true,
              prefix = storageGetPrefix(),
              i, key;
      for (i = 0; i < keys.length; i++) {
        key = keys[i] = prefix + keys[i];
        if (key.substr(0, 3) != 'xt_' && cache[key] !== undefined) {
          result.push(cache[key]);
        }
        else if (useLs) {
          try {
            value = localStorage.getItem(key);
          } catch (e) {
            useLs = false;
          }
          try {
            value = (value === undefined || value === null) ? false : JSON.parse(value);
          } catch (e) {
            value = false;
          }
          result.push(cache[key] = value);
        }
        else if (!useCs) {
          result.push(cache[key] = false);
        }
        else {
          allFound = false;
        }
      }
      if (allFound) {
        return callback(single ? result[0] : result);
      }
    }
    function storageSetValue(obj, callback) {
      var keyValues = {},
              prefix = storageGetPrefix(),
              key, value;
      for (key in obj) {
        if (obj.hasOwnProperty(key)) {
          value = obj[key];
          key = prefix + key;
          cache[key] = value;
          value = JSON.stringify(value);
          if (useLs) {
            try {
              localStorage.setItem(key, value);
            } catch (e) {
              useLs = false;
            }
          } else {
            keyValues[key] = value;
          }
        }
      }
      if (useLs || !useCs) {
        if (callback) {
          callback();
        }
      }
    }
    function storageRemoveValue() {
      var keys = Array.prototype.slice.call(arguments),
              prefix = storageGetPrefix(),
              i, key, callback;
      if (typeof keys[keys.length - 1] === 'function') {
        callback = keys.pop();
      }
      for (i = 0; i < keys.length; i++) {
        key = keys[i] = prefix + keys[i];
        delete cache[key];
        if (useLs) {
          try {
            localStorage.removeItem(key);
          } catch (e) {
            useLs = false;
          }
        }
      }
      if (callback) {
        callback();
      }
    }
    window.ConfigStorage = {
      prefix: storageSetPrefix,
      noPrefix: storageSetNoPrefix,
      get: storageGetValue,
      set: storageSetValue,
      remove: storageRemoveValue
    }
  })(window);