Redux lesson 02

Redux-lesson-01.js

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 render = () => {
	//method 1
  document.body.innerText = store.getState();
}

//constructor
const store = createStore(counter);

//method 3
const s = store.subscribe(render);
console.log(s());
render();

document.addEventListener("click", () => {
	//method 2
  store.dispatch({ type: 'INCREMENT'});
});