@zedux/core/dist/esm/api/createReducer.js

A high-level, declarative, composable form of Redux

import { extractActionType, extractActionTypes } from '../utils/actions.js';
/**
  Creates a new ReducerBuilder.

  A ReducerBuilder is just a reducer with a special `.reducer()` method for
  easily mapping action types to sub-reducers that handle them.
*/
export const createReducer = (initialState) => {
    const actionToReducersMap = {};
    const reducer = ((state = initialState, action) => {
        const reducers = actionToReducersMap[action.type] || [];
        return runReducers(reducers, state, action);
    });
    reducer.reduce = (reactable, subReducer) => {
        const method = 'ReducerBuilder.reduce()';
        const actionTypes = Array.isArray(reactable)
            ? extractActionTypes(reactable, method)
            : [extractActionType(reactable, method)];
        mapActionTypesToReducer(actionToReducersMap, actionTypes, subReducer);
        return reducer;
    };
    return reducer;
};
const mapActionTypesToReducer = (map, actionTypes, consumer) => {
    actionTypes.forEach(actionType => {
        if (!map[actionType]) {
            map[actionType] = [];
        }
        map[actionType].push(consumer);
    });
};
const runReducers = (reducers, state, action) => {
    return reducers.reduce((accumulatedState, reducer) => reducer(accumulatedState, action.payload, action), state);
};