Utility method that allows to create a Redux middleware and execute custom code before or after an action is dispatched.

create_middleware.js

import * as Immutable from 'immutable';
// Helper method for creating a middleware that handles the given set of actions
export function createMiddleware(handlers) {
  return storeAPI => next => action => {
    const actionHandler = Immutable.List(handlers).find(h => h.action.type === action.type);
    // Execute custom middleware handler before the action is dispatched
    if (actionHandler && actionHandler.beforeHandler) {
      actionHandler.beforeHandler(storeAPI, action);
    }
    // Dispatch the action
    const result = next(action);
    // Execute custom middleware handler after the action is dispatched
    if (actionHandler && actionHandler.afterHandler) {
      actionHandler.afterHandler(storeAPI, action);
    }
    return result;
  }
}

See full blogpost 'Navigation Redirects Through Redux Middleware'