eggheadio-projects/getting-started-with-redux: null

<!DOCTYPE html>
<html>
<head>
 <meta charset="utf-8">
 <title>Plunker</title>
 <script src="https://unpkg.com/react@16.3.2/umd/react.production.min.js"></script>
 <script src="https://unpkg.com/react-dom@16.3.2/umd/react-dom.production.min.js"></script>
 <script src="https://unpkg.com/babel-standalone@6.26.0/babel.min.js"></script>

 <script src="https://unpkg.com/redux@4.0.0/dist/redux.js"></script>
 <script src="https://unpkg.com/react-redux@5.0.7/dist/react-redux.js"></script>
</head>
<body>
 <div id='root'></div>
 <script type="text/jsx" src="script.jsx"></script>
</body>
</html>

const counter = (state = 0, action) => {
  switch (action.type) {
    case 'INCREMENT':
      return state + 1;
    case 'DECREMENT':
      return state - 1;
    default: 
      return state;
  }
}

const createStore = (reducer) => {
  let state;
  let listeners = [];
  
  const getState = () => state;
  
  const dispatch = (action) => {
    state = reducer(state, action);
    listeners.forEach(listener => listener());
  };
  
  const subscribe = (listener) => {
    listeners.push(listener);
    return () => {
      listeners = listeners.filter(l => l !== listener);
    };
  };
  
  dispatch({});
  
  return { getState, dispatch, subscribe };
};

const store = createStore(counter);

const render = () => {
  document.body.innerText = store.getState();
};

store.subscribe(render);
render();

document.addEventListener('click', () => {
  store.dispatch({ type: 'INCREMENT' });
});