SOURCE

class createStore {
  private state = {}
  reducer = {}
  listeners = []
  constructor(reducer, state) {
    this.reducer = reducer 
    this.state = state
  }
  dispatch(action) {
    this.state = this.reducer(this.state, action)
    this.listeners.forEach(listener => listener())
  }
  subscribe(listener) {
    this.listeners.push(listener)
    return () => {
      this.listeners = this.listeners.filter(l => l !== listener)
    }
  }
  getState() {
    return this.state
  }
}

let defaultState = {
  t1:1
}

let reducer1 = function ((state = defaultState, action)){
   const _currentState = {
      ADD_CHAT: () => {
          state.mm = 20;
          state.d2 = Object.assign({}, action.data);
          return state;
      }
  };
  return _currentState[action.type] && _currentState[action.type]();
}



let store1 = new createStore(reducer1)

store1.subscribe(function(){
  console.log('subscribe')
})

store1.dispatch({
  type: 'ADD_CHAT',
  data: {
    a: 2
  }
})