Skip to main content

Action Creator Middleware

A custom middleware that detects if an action creator has been mistakenly dispatched, instead of being called before dispatching.

A common mistake is to call dispatch(actionCreator) instead of dispatch(actionCreator()). This tends to "work" as the action creator has the static type property, but can lead to unexpected behaviour.


export interface ActionCreatorInvariantMiddlewareOptions {
* The function to identify whether a value is an action creator.
* The default checks for a function with a static type property and match method.
isActionCreator?: (action: unknown) => action is Function & { type?: unknown }



Creates an instance of the action creator check middleware, with the given options.

You will most likely not need to call this yourself, as getDefaultMiddleware already does so. Example:

import {
} from '@reduxjs/toolkit'
import reducer from './reducer'

// Augment middleware to consider all functions with a static type property to be action creators
const isActionCreator = (
action: unknown
): action is Function & { type: unknown } =>
typeof action === 'function' && 'type' in action

const actionCreatorMiddleware = createActionCreatorInvariantMiddleware({

const store = configureStore({
middleware: () => new Tuple(actionCreatorMiddleware),