quick redux from scratch

function createStore(reducer, preloadedState) {
  let state = preloadedState;
  let listeners = [];
  
  const subscribe = (callback) => {
    listeners = [...listeners, callback];
    return function () {
      listeners = listeners.filter(f => f !== callback);
    }
  }
  
  const dispatch = (action) => {
    state = reducer(state, action);
    listeners.forEach(f => f(state));
  }
  
  return {
    subscribe,
    dispatch
  }
}