reducer.js

const listReducer = (state = initialState, action) => {
    switch(action.type) {
        case UPDATE_LIST:
            return {
                ...state,
                postobject: action.payload,
                list: [...state.list.filter(
                    object => object.id !== action.payload.id
                ), action.payload] 
            };
        default:
            return state
    }
}