Can I pass simple arrays in redux state?

I started to learn better redux + reactjs

For example I have a news or list reducer that should return an array contain news items :

const list = [
    {id: 1, title: 'One'},
    {id: 2, title: 'Two'},
    {id: 3, title: 'Three'}

export function newsReducer(state = [], action) {
    switch (action.type) {
        case 'GET_NEWS':
            return list
            return state

This code works right, but in other articles I saw they passed parameters with [...state, ...] and immutable format ...

So can I pass parameters simple or I should pass in immutable format ?


In short: Yes you can pass simple arrays in if that suits your needs best.

If you are going to use a simple array, then make sure to return a new array when making modifications.

For example:

export function listChangeReducer = (state = [], action) => {
  switch action.type {
    case 'ADD_ITEM':
      // don't do this because you're mutating your state
      // state.push(action.item);
      // instead do this
      state = state.slice();
      // or alternatively you can use the destruct syntax
      //[...state, action.item];
      return state;


You aren't required to use immutablejs data structures with redux. It is just recommended so that you don't accidentally mutate your data structures.

The documentation states that the data needs to be immutable because

Both Redux and React-Redux employ shallow equality checking. In particular:

Redux's combineReducers utility shallowly checks for reference changes caused by the reducers that it calls.