Vanilla Javascript flux implementation. Easy to understand and copy into your own project, modifying and extending as necessary.

Flux Architecture Base (Vanilla JS)

const createStore = (reducer, initialState) => {
  const subscribers = [];
  let currentState = initialState;
  
  return {
    getState: () => currentState,
    subscribe: fn => {
      subscribers.push(fn);
      fn(currentState);
    },
    dispatch: action => {
      currentState = reducer(currentState, action);
      subscribers.forEach(fn => fn(currentState));
    }
  };
};

/* 
 * With native functions like Object.assign, references to 
 * other objects are copies as refences. To create clones of the 
 * referenced object's properties and values, we need to 
 * stringify the object, then parse it: 
*/
const deepCopy = object => JSON.parse(JSON.stringify(object));

const reducer = (state, action) => {
  let newState = deepCopy(state);
  if(action.type === 'INCREMENT') {
    newState.count++;
    return newState;
  } else if (action.type === 'DECREMENT') {
    newState.count--;
    return newState;
  } else {
    return state;
  }
};
  
  
let state = {
  count: 1
};

let store = createStore(reducer, state);

let incrementAction = {
  type: 'INCREMENT'
};

let decrementAction = {
  type: 'DECEREMENT'
};

console.log('Initial: ', store.getState());

store.dispatch(incrementAction);

console.log('After incn action: ', store.getState());