simple reducer with error using immutable data

formReducer.js

const initialState = Map({
  is_loading: false,
  is_finish: null,
  error: {
    code: '',
    message: '',
  },
});

const formReducer = (state = initialState, action) => {
  switch (action.type) {
    case FORM.START_POST:
      return state.withMutations(state =>
        state.set('is_loading', true)
              .set('error', Map())
              .set('is_finish', false)
      );
    case FORM.SUCCESS_POST:
      setTimeout(() => state.set('is_finish', false), 2500);
      return state.withMutations(state =>
        state.set('is_loading', false)
              .set('error', Map())
              .set('is_finish', true)
      );
    case FORM.FAILED_POST:
      setTimeout(() => state.set('is_error', false), 2500);
      setTimeout(() => state.set('is_finish', false), 2500);
      return state.withMutations(state =>
        state.set('is_loading', false)
              .set('error', fromJS({action.message, action.code})
              .set('is_finish', true)
      );
    default:
      return state;
  }
};