In Redux, is it necessary to do deep copy

Question

The below object is action.data has a nested object address

{
    name: 'Ben',
    address: {
        country: 'Australia',
        state: 'NSW'
    }
}

How should I handle it in the reducer?

const rootReducer = (state = initState, action) {
    switch(action.type) {
        switch RECEIVE_DATA:
            return {...state, data: action.data}
    }
}

Can I do it as above? that I just assign the whole object to data without copying?

or

const rootReducer = (state = initState, action) {
    switch(action.type) {
        switch RECEIVE_DATA:
            const address = {...action.data.address}
            const data = {...action.data, address}
            return {...state, data}
    }
}

Or should I do a deep copy of the object and assign it to data? thanks

Answer 1

The "correct" way to handle updates of nested data is with multiple shallow copies, one for each level of nesting. It's also certainly okay to create a new object that just replaces one field completely, per your first example.

See the Redux docs section on Immutable Update Patterns for some info on how to properly do immutable updates, and also the Redux FAQ entry regarding deep cloning.

Answer 2

From Redux:

Common Redux misconception: you need to deeply clone the state. Reality: if something inside doesn't change, keep its reference the same!