What is correct way to update nested objects in redux

Question

I was reading this redux documentation . https://redux.js.org/usage/structuring-reducers/immutable-update-patterns .

please see the below code

function insertItem(array, action) {
  return [
    ...array.slice(0, action.index),
    action.item,
    ...array.slice(action.index)
  ]
}

they are using the slice method for updating the state and but what if state looks like below

const state = [{name:"x1",obj:{}},{name:"x2",obj:{}},{name:"x3",obj:{}}];

let y = {...state.slice(1)};

console.log(state[1]['obj'] === y[0]['obj']) // true
console.log(state[2]['obj'] === y[1]['obj']) // true 

is it ok to update states in this way . or it is wrong as we are updating state directly we can see in console.log our new state still point to old state nested object references . or copying old state refrence while making new state is fine . does not cause any issue .

I see one question on stackoveflow . I commented on the solution . that was also refrencing the old state .

Adding Object to nested array in react-redux

let state = {
    items : {
        deepItem  :[1, 2, 2],
        reallyDeepItem: {
            a : [1,2,3],
            b : ['a', 'c']
        }
    }
};

let x = {
            ...state,
            items : {
                ...state.items,
                deepItem : state.items.deepItem.concat(3)
            }
        }


console.log(x.items === state.items) // false
console.log(x.items.reallyDeepItem === state.items.reallyDeepItem) // true (still pointing the old reference ) 
console.log(x.items.deepItem === state.items.deepItem) //false

I know we can use Immerjs and reduxtool kit but i want to understand how to update immutable state correctly .

Answer 1

this link explain this question . https://catwolf.org/qs?id=3f201d2d-da9f-4019-88ab-566a765b7835&x=y

Common Redux misconception: you need to deeply clone the state. Reality: if something inside doesn't change, keep its reference the same! below is doc link. https://redux.js.org/faq/performance#do-i-have-to-deep-clone-my-state-in-a-reducer-isnt-copying-my-state-going-to-be-slow