Redux Quick Start Guide

Reducers

Next, we need to write reducers. The following reducer is using Immutable JS:

import { List, Map } from "immutable";import { combineReducers } from "redux";import * as types from "../constants/ActionTypes";function todoList(state = List(), action) {  switch (action.type) {    case types.ADD_TODO:      return state.push(        Map({          id: action.id,          text: action.text,          isCompleted: false        })      );    case types.COMPLETE_TODO:      return state.map(todo => {        if (todo.get("id") === action.id) {          return todo.update("isCompleted", v => !v);        }        return todo;      });    case types.DELETE_TODO:      return state.filter(todo => todo.get("id") !== action.id);    case types.DELETE_ALL_TODOS:      return state.clear();    default:      return state;  }}function activeFilter(state = "all", action) { switch ...