Redux + Immutable.Map

genesis.js

import { Map } from "immutable";

// reducers
const INITIAL_STATE = Map({ post: null, isLoading: false });

function postReducer(state = INITIAL_STATE, action) {
  switch (action.type) {
    case "FETCHED": {
      return state.withMutations(currentState =>
        currentState.set("post", action.payload.post).set("isLoading", false),
      );
    }
    default: {
      return state;
    }
  }
}

// action creators
function fetchedPost(post) {
  return {
    type: "FETCHED",
    payload: {
      post,
    },
  };
}