const ADD = 'ADD';

const reducer = (state = 0, action) => {
  switch(action.type) {
    case ADD:
      return state + 1;
    default:
      return state;
  }
};

const store = Redux.createStore(reducer);

// global count variable:
let count = 0;

// change code below this line
store.subscribe(function() {  //this callback function will run every time that the store receives an action.  In this case, it would also change the global variable.
  count += 1;
})

// change code above this line

store.dispatch({type: ADD});
console.log(count);
store.dispatch({type: ADD});
console.log(count);
store.dispatch({type: ADD});
console.log(count);