code: function getItem$2(key, callback) {
      var self = this;
  
      key = normalizeKey(key);
  
      var promise = self.ready().then(function () {
          var dbInfo = self._dbInfo;
          var result = localStorage.getItem(dbInfo.keyPrefix + key);
  
          // If a result was found, parse it from the serialized
          // string into a JS object. If result isn't truthy, the key
          // is likely undefined and we'll pass it straight to the
          // callback.
          if (result) {
              result = dbInfo.serializer.deserialize(result);
          }
  
          return result;
      });
  
      executeCallback(promise, callback);
      return promise;
  }
docs: Retrieve an item from the store. Unlike the original async_storage library in Gaia, we don't modify return values at all. If a key's value is `undefined`, we pass that value to the callback function.