To prevent out-of-sync React Redux toolkit dispatches or just plain react.js in general which could result in unexpected behaviors due to asynchronous server requests returning at different times, we need to ensure that we handle component unmounts or updates correctly. This ensures that when a component re-renders or unmounts, for several reasons like a user clicks on another link related to the same component, it does not attempt to set state based on outdated or irrelevant asynchronous responses.

This weird behaviour could result in items from the old server request being rendered or screen flicks happening.

Let’s break down the example code below analyze its current behavior:


  1. Immediate Re-renders: If route or dispatch change frequently, it may cause the useEffect to re-run multiple times in quick succession, potentially leading to multiple pending asynchronous requests. This can result in race conditions where responses are handled in an unexpected order.
import { useState, useEffect } from 'react';
import { useParams } from "react-router-dom";

function MyComponent({ route, dispatch }) {
  const [postData, setPostData] = useState({ title: '', body: '' });
  const route = useParams();

  useEffect(() => {
    let isMounted = true; // Tracks whether the component is still mounted

    if (! {

    const fetchData = async () => {
      try {
        const response = await dispatch(fetchPost(Number.parseInt(, 10))).unwrap();
        if (isMounted) { // Only update state if still mounted
          setPostData({ title: response.title, body: response.body });
      } catch (error) {
        console.log("Error fetching post");


    return () => {
      isMounted = false; // Set flag to false on cleanup
      console.log("Clearing Use effect");
  }, [, dispatch]); // Only re-run if or dispatch changes

  return (

How it works and Solution:

  1. isMounted Flag: Using a flag (isMounted) to check if the component is still mounted before updating the state ensures that the component does not attempt to update its state after it has been unmounted.

  2. Dependency Array: Only includes and dispatch, reducing unnecessary re-renders.

  3. Cleanup Function: On component unmount or dependency change, the cleanup function runs, setting isMounted to false. This ensures that any ongoing asynchronous operation does not attempt to update the state if the component is no longer mounted or if the dependencies have changed.


Using a flag to track whether the component is still mounted before updating the state within an asynchronous operation ensures that state updates are only attempted when the component is active. This prevents the weird behaviors that can arise from asynchronous operations trying to update an unmounted or quickly re-rendered component.