Redux but without support for middleware

reredux.js

class Store {
  constructor(reducer, preloadedState = undefined) {
    this.reducer = reducer;
    this.state = reducer(preloadedState, { type: '@@INIT' });
    this.listeners = [];
  }

  getState() {
    return this.state;
  }

  dispatch(action) {
    this.state = this.reducer(this.state, action);
    for (let listener of this.listeners) {
      listener();
    }
    return action;
  }

  subscribe(listener) {
    this.listeners = this.listeners.concat(listener);
    return () => {
      const index = this.listeners.indexOf(listener);
      this.listeners.splice(index, 1);
    };
  }

  replaceReducer(nextReducer) {
    this.reducer = nextReducer;
  }
}

export function createStore(reducer, preloadedState) {
  return new Store(reducer, preloadedState);
}