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https://redux.js.org/recipes/structuring-reducers/reusing-reducer-logic How to use the reusable reducers ...

JS Docs

Currently, there is stringReducer, booleanReducer, listReducer and objectReducer ...

import { 
    listReducer, 
    objectReducer,
    stringReducer,
    booleanReducer,
} from "@wecreatesoftware/redux-higher-order-reducers"
import { 
    LIST_A, 
    LIST_B, 
    LIST_C, 
    OBJECT_A, 
    OBJECT_B,
    STRING_A,
    STRING_B,
    BOOLEAN_A,
} from "../some/constant/file"

export const reducers = combineReducers({
    [ LIST_A ]: listReducer({ reducerName: LIST_A }),
    [ LIST_B ]: listReducer({ reducerName: LIST_B }),
    [ LIST_C ]: listReducer({ 
        reducerName: LIST_C, 
        key: "id",
    }),
    [ OBJECT_A ]: objectReducer({ reducerName: OBJECT_A }),
    [ OBJECT_B ]: objectReducer({ reducerName: OBJECT_B }),
    [ STRING_A ]: stringReducer({ reducerName: STRING_A }),
    [ STRING_B ]: stringReducer({ reducerName: STRING_B }),
    [ BOOLEAN_A ]: booleanReducer({ reducerName: BOOLEAN_A }),
})

Now that the store has the reducer, we need to dispatch actions. Everything is the same as usual but now we need to tell the action which "reducer" to update.

List Reducer

addItemAction({ 
    reducerName: LIST_A, 
    item: { id: 1 },
})

addItemsAction({ 
    reducerName: LIST_A, 
    items: [ { id: 1 } ],
})

insertItemAction({ 
    reducerName: LIST_A, 
    item: { id: 1 }, 
    index: 3,
})

removeItemAction({
    reducerName: LIST_A, 
    index: 3,
})

removeItemByKeyAction({ 
    reducerName: LIST_C, 
    item: { id: 1 },
})

updateItemAction({ 
    reducerName: LIST_A, 
    item: { 
        id: 1, 
        newKey: "newValue" 
    }, 
    index: 3,
})

updateItemByKeyAction({ 
    reducerName: LIST_C, 
    item: {
        id: 1, 
        foo: "bar" 
    },
})

updateItemsByKeyAction({ 
    reducerName: LIST_C, 
    items: [ 
        {
            id: 1, 
            foo: "bar" 
        }, 
        {
            id: 2, 
            cool: "beans" 
        },
    ] 
})

updateValueAllItemsAction({ 
    reducerName: LIST_C, 
    keyValuePairs: {
        foo: bar,
        updated: true,
        collapsed: true,
    }
})

resetListAction({ reducerName: LIST_A }))

setListAction({ 
    reducerName: LIST_A, 
    payload: [],
})

Object Reducer

updateObjectAction({ 
    reducerName: OBJECT_A, 
    payload: { loading: true }, 
})

resetObjectAction({ reducerName: OBJECT_A })

setObjectAction({ 
    reducerName: OBJECT_B, 
    payload: {},
})

String Reducer

resetStringAction({ reducerName: STRING_A })

setStringAction({ 
    reducerName: STRING_B, 
    payload: "foo bar",
})

Boolean Reducer

resetBooleanAction({ reducerName: BOOLEAN_A })

setBooleanAction({ 
    reducerName: BOOLEAN_A, 
    payload: true,
})

toggleBooleanAction({ reducerName: BOOLEAN_A })

It might be annoying constantly setting reducer name right? I certainly think so ... If you agree, you can do a curry function for each action for your reducers as follows.

import { 
    objectReducer, 
    updateObjectAction 
} from "@wecreatesoftware/redux-higher-order-reducers"
import { SOME_NAME } from "../some/constant/file"

export const reducers = combineReducers({
    [ SOME_NAME ]: objectReducer({ reducerName: SOME_NAME }),
})

export const updateSomeNameAction = payload => updateObjectAction({ 
    reducerName: SOME_NAME,
    payload,
})

dispatch(
    updateSomeNameAction({ 
        loading: false, 
        cool: "beans", 
        foo: "bar",
    })
)

Extended Reducer

Have an edge case that just can't be covered by the basic actions/cases? The idea for extendedReducer allows you to give your own custom reducer to the higher order reducer with your own action/cases. Lets have a look ...

import { objectReducer } from "@wecreatesoftware/redux-higher-order-reducers"
import { SOME_NAME } from "../some/constant/file"

const extendedReducer = (state, { type, payload }) => {
    switch (type) {
        case "MY_CUSTOM_ACTION":
            return {
                ...state,
                ...payload,
                lastUpdated: new Date().getTime(),
            }
        default:
            return state
    }
}

export const reducers = combineReducers({
    [ SOME_NAME ]: objectReducer({ 
        reducerName: SOME_NAME, 
        extendedReducer,
    }),
})

export const myCustomAction = payload => ({ 
    type: "MY_CUSTOM_ACTION", 
    payload,
    meta: { reducerName: SOME_NAME },
})

dispatch(myCustomAction({ 
    loading: false, 
    cool: "beans", 
    foo: "bar",
}))

The above dispatch will flow through the higher order reducer, find no case, fall into default case, and then call the extendedReducer, allowing the extended reducer to do any sort of logic to the state.

Here it will return ...

state = {
    loading: false, 
    cool: "beans", 
    foo: "bar",
    lastUpdated: 1554174417035, //timestamp of when it was updated 
}

The above capabilty also helps with middleware checking for a specific type asthe higher order reducer uses the same generic action for updates.

Each reducer, consider it like a micro service, it does one thing and one thing well.

With a reducer handling very specific data, adding a library like reselect makes it easy to select, combine, filter data. Making selectors to get specific pieces of data allows you to select the exact information needed for the given component, vs giving the component some high level object and use a couple keys from it.

The selectors can easily make dumb components. If where data was stored was, changed, the selectors can be easily updated without the components even knowing anything about the data structure... it also can clean up components by not having to do a lot of null checks. Using default props to set lists to empty, bools to false/true, etc will allow destructured props not break in random scenarios.

cannot destructure property of 'undefined' or 'null'

The usage of the higher order reducers are endless, you just have to be created. I have been using them for a short time, and it has made my life a lot easier. Little to no duplicate data, creating new components and getting data has been easy, and I never have to write crud reducers, reducer tests, actions, action tests anymore ;) !!

Demo:

cd demo
npm run demo