replacement.js

import _ from 'lodash';

export function replacementReducer(actionType, defaultVal) {
    if (defaultVal === undefined) {
        throw new Error(
            `No default value passed to replacementReducer for action type ${actionType}`
        );
    }

    return (state = defaultVal, action = {}) => {
        if (action.type === actionType) {
            let newValue = action.payload;
            let oldValue = state;
            if (_.isEqual(newValue, oldValue)) {
                // don't kill off shallow comparison of array objects if they are equal
                return state;
            }
            return action.payload;
        }
        return state;
    };
}