Adding and removing reducers to redux dynamically using an event listener system

event_listeners.js

import {desktopNotify, requestDesktopNotify} from '@/util/browser'


// when user clicks "notify me" checkbox
requestDesktopNotify()
store.dispatch({
    type: 'ADD_EVENT_LISTENER',
    pattern: 'ALERT',
    handler: (action) => {
        if (action.alert.subtype == 'sit_in')
            desktopNotify(action.alert.message)
    },
})


const actionMatchesListener = (listener, action) => {
    // exact string pattern
    if (typeof(listener.pattern) === 'string')
        return listener.pattern === action.type

    // regex pattern
    if (listener.pattern.test))
        return listener.pattern.test(action.type)

    // function pattern
    if (typeof(listener.pattern === 'function'))
        return listener.pattern(action)

}

const matchingListeners = (listeners, action) =>
    Object.values(listeners).filter(listener => 
        actionMatchesListener(action, listener))


const eventsReducer = (state, action) => {
    switch(action.type) {
        case 'ADD_EVENT_LISTENER':
            const len = Object.keys(state).length
            return {
                ...state,
                [action.id || len]: action.handler,
            }
        default:
            // run all redux actions through eventListeners
            for (let listener of matchingListeners(state, action)) {
                listener.handler(action)
            }
            return state
    }
}