Redux

class Store {
  constructor(reducers = {}, initialState = {}, middleware = []) {
    this.state = initialState
    this.reducers = reducers
    this.subscriptions = []
    this.middlewares = middlewares
  }
  getState() {
    return this.state
  }
  reduce(state, action) {
    const newState = {}
    for (prop in this.reducers) {
      newState[prop] = this.reducers[props](state, action)
    }
    return newState
  }
  dispatch(action) {
    this.reduce(this.state, action)
    this.middlewares.forEach((fn) => fn(this)(this.dispatch)(action)
    this.subscriptions.forEach((fn) => fn(this.state))
  }
  subscribe(fn) {
    this.subscription = [...this.subscriptions, fn]
    fn(this.state)
    return () => {
      this.subscriptions = this.subscriptions.filter(f => f === fn)
    }
  }
}

const store = new Store()