extend(obj1, obj2) {
      for (var i in obj2) {
        if (obj2.hasOwnProperty(i)) {
          obj1[i] = obj2[i]
        }
      }
      return obj1
    }
Simple object extend function
@param   { Object } obj1 - destination
@param   { Object } obj2 - source
@returns { Object } - destination object