index.reducer.js

const SignListByIdReducer = (state = { }, action) => {
  switch (action.type) {
    case actions.SUBMIT_EMAIL:
      return Object.assign({}, state, {
        [action.id]: {
          id: action.id,
          email: action.email,
          list: action.list,
          loading: true,
          errors: [],
        }
      });
    case actions.EMAIL_ADDED:
      console.log('EMAIL_ADDED', state, action);
      return Object.assign({}, state, {
        [action.id]: Object.assign({}, state[action.id], {
          loading: false,
          errors: [],
        }),
      });
    case actions.FAIL_TO_ADD:
      return Object.assign({}, state, {
        [action.id]: Object.assign({}, state[action.id], {
          loading: false,
          errors: action.errors,
        }),
      });
    default:
      return state;
  }
};