Simple Redux Implementation

example.js

const reducer = (state, action) => action.type == 'INC' 
  ? Object.assign({}, state, { counter: state.counter + 1 })
  : state;

const store = createStore(reducer, { counter: 1 });

const unsubscribe = store.subscribe(() => console.log('Counter: ' + store.getState().counter));

store.dispatch({ type: 'INC' })
store.dispatch({ type: 'INC' })

unsubscribe();

store.dispatch({ type: 'INC' })

redux.js

class Store {
  constructor(reducer, state) {
    Object.assign(this, { state, reducer, cbs: [] });
  }
  
  getState() { 
    return this.state 
  }
  
  dispatch(action) {
    this.state = this.reducer(this.state, action);
    this.cbs.forEach(cb => cb()); 
  }
  
  subscribe(cb) {
    this.cbs.push(cb);
    
    return () => {
      this.cbs = this.cbs.filter(i => i !== cb);
    }
  }
}

const createStore = (reducer, initialState) => new Store(reducer, initialState);