MusareReact/frontend/app/js/reducers/app.js

import { Map } from "immutable";

import {
  TEST_ACTION,
  TEST_ASYNC_ACTION_START,
  TEST_ASYNC_ACTION_ERROR,
  TEST_ASYNC_ACTION_SUCCESS,
} from "actions/app";

const initialState = Map({
	counter: 0,
	asyncLoading: false,
	asyncError: null,
	asyncData: null,
});

const actionsMap = {
	[TEST_ACTION]: (state) => {
		const counter = state.get("counter") + 1;

		return state.merge({
			counter,
		});
	},

  // Async action
	[TEST_ASYNC_ACTION_START]: (state) => {
		return state.merge({
			asyncLoading: true,
			asyncError: null,
		});
	},
	[TEST_ASYNC_ACTION_ERROR]: (state, action) => {
		return state.merge({
			asyncLoading: false,
			asyncError: action.data,
		});
	},
	[TEST_ASYNC_ACTION_SUCCESS]: (state, action) => {
		return state.merge({
			asyncLoading: false,
			asyncData: action.data,
		});
	},
};

export default function reducer(state = initialState, action = {}) {
	const fn = actionsMap[action.type];
	return fn ? fn(state, action) : state;
}