Why isn't state being updated with a reducer using Object.assign?

I'm trying to create a reducer without the benefit of ES6. It's an old PHP app with no build process to leverage for transpilation.

I'm initializing state:

let defaultState =  {
    accountTypes: {
        personal: {
            selected: false,
            checking: {
                selected: false
            },
            savings: {
                selected: false
            }
        },
        business: {
            selected: false,
            checking: {
                selected: false
            },
            savings: {
                selected: false
            }
        }
    }
};

Here's the reducer and then the store init:

function reducer(state, action) {
  switch (action.type) {
    case 'TOGGLE_ACCOUNT_TYPE':
      console.log(state.accountTypes);
      // {
      //   business: {selected: false, checking: {…}, savings: {…}}
      //   personal: {selected: true}
      // }

      console.log(action.payload);
      // {
      //   personal: {selected: true}
      // }

      let blah = Object.assign({}, state, {
        accountTypes: Object.assign({}, state.accountTypes, action.payload)
      });

      console.log(blah.accountTypes);
      // {
      //   business: {selected: false, checking: {…}, savings: {…}}
      //   personal: {selected: true}
      // }

      return blah;

    default:
      return state;
  }
}

const store = Redux.createStore(reducer, defaultState);
let state = store.getState();

Subscribing to state later, inside jQuery's document.ready:

store.subscribe(function () {
    console.log(state.accountTypes);
    // {
    //    business: {selected: false, checking: {…}, savings: {…}}
    //    personal: {selected: false, checking: {…}, savings: {…}}
    // }

You can see that the state isn't updated with the action payload.

I think I've just stumbled on my answer. Posting the question jarred something loose. I was using a stale state variable for my jQuery operations.

store.subscribe(function () {
    // update the state var
    state = store.getState();

If there's a better way to use a state variable without having to manually refresh it, please post another answer.