Change only one value and keep other intact Redux

Question

A lot of answered question about how to change a single value, but I still can't figure it out how to change only type value only for Mac and keep other values intact.

const initialStateMac = {
    type: MacBook,
    os: MacOS
};

const initialStatePc = {
    type: Laptop,
    os: Windows
};

const rootReducer = combineReducers({
    mac: macReducers,
    pc: pcReducers
});

const store = createStore(rootReducer);

export const Mac = (state = initialStateMac, action) => {
    switch (action.type) {
        case "SET_DEVICE_TYPE":
            return {
                ...state,
                type: action.payload
            };
        default:
            return state;
    }
};

export const Pc = (state = initialStatePc, action) => {
    switch (action.type) {
        case "SET_DEVICE_TYPE":
            return {
                ...state,
                type: action.payload
            };
        default:
            return state;
    }
};

{
    type: "SET_DEVICE_TYPE",
    payload: "ddd"
}

to be clear, I want get:

    Mac: {
        type: ddd,
        os: MacOS
    },
    Pc: {
        type: Laptop,
        os: Windows
    }

but not:

    Mac: {
        type: ddd,
        os: MacOS
    },
    Pc: {
        type: ddd,
        os: Windows
    }

Answer 1

In case with multiple reducers just using different action types for every reducer correspondingly would be the easiest solution

The answer below was given with the assumption that 1 reducer was used with initalState {Mac: {type: "", os: ""}, PC: {type: "", os:""}}

If you want to specifically change type attribute of the object with "Mac" key You could use this.

export default (state = intialState, action) => {
    switch (action.type) {
        case "SET_DEVICE_TYPE":
            const {Mac} = state;
            return {
                ...state,
                Mac: {
                   ...Mac,
                   type: action.payload
                }
            };
        default:
            return state;
    }
};

Note: If you want to specifically change type attribute of the object with "Mac" key, then would be better if the action type was like "SET_MAC_DEVICE_TYPE"

Also if the key need to be dynamic -

// action.payload = {key: "Mac", type: "ddd"}

export default (state = intialState, action) => {
    switch (action.type) {
        case "SET_DEVICE_TYPE":
            const initValue = state[action.payload.key];
            return {
                ...state,
                [action.payload.key]: {
                   ...initValue,
                   type: action.payload.type
                }
            };
        default:
            return state;
    }
};

Answer 2

Pass initialState.Mac into the reducer as the default state

export default (state = initialState.Mac, action) => {
    switch (action.type) {
        case "SET_DEVICE_TYPE":
            return {
                ...state,
                type: action.payload
            };
        default:
            return state;
    }
};