const {createStore} = require("redux");
const initialState = { age:21 };
const myReducer = (state = initialState, action) =>
{
    if(action.type === 'ADD'){ state.age += 1;  }

    // console.log('Hello' );
    // console.log(JSON.stringify(state) );
    // console.log(state.age);

    return  state;
}
const store = createStore(myReducer);
store.dispatch({type: 'ADD'});
store.subscribe(()=>{

    console.log('Hello' );
    console.log(JSON.stringify(store) );
    console.log(store.age);

});
store.dispatch({type: 'ADD'});

node redrec.js

Hello
{}
undefined

Hello
{"age":21}
21
Hello
{"age":22}
22
Hello
{"age":23}
23
Hello
{}
undefined