Introduction:

In React and Redux applications, managing state efficiently is crucial for optimal performance. One common issue developers face is the persistence of reducer state in useSelector hooks, causing unnecessary re-renders even when actions are not called. In this article, we'll explore the importance of resetting the reducer state and how to implement it in your application.

Section 1: Understanding the Problem

The useSelector hook is a powerful tool in Redux that allows components to access the Redux store's state. However, when the reducer state is not reset, useSelector can cause unnecessary re-renders, impacting performance. Consider the following example:

import { useDispatch, useSelector } from "react-redux";
import {useState,useEffect} from "react";
import {addUser} from "../actions";

function Page(){
const dispatch = useDispatch()
const user = useSelector((state) => state.user);
const addUser = useSelector((state) => state.addUser);
//setting a snackbar for user to see the response on adding the new user
const [snackBarIsOpen, setSnackBarIsOpen]=useState(false);
const [snackMsg, setSnackBarMsg] = useState("");
const [usersData, setUsersData] = useState([]);
useEffect(() => {
  if (user.response) {
    setUserData(user.response.data)
  }
}, [user]);
useEffect(() => {
  if (addUser.response) {
    setSnackBarIsOpen(true)
    setSnackBarMsg(addUser.response.message)
  }
 if (addUser.error) {
    setSnackBarIsOpen(true)
    setSnackBarMsg(addUser.error.data.message)
  }
}, [addUser]);

function addUserButton(name){
   dispatch(addUser(name))       //dispatching the action
}

/*
//remaining code
*/

In the above example, we are retrieving a user list from reducers and rendering it on a Page along with an 'Add' button to add a user. If it is a new user, it will be added to the list with the message User added successfully.However, if it is a duplicate user, an error message Duplicate user not allowed will be displayed. In this scenario, a snackbar is used to show the messages. Additionally, we are considering the use of redux-persist to maintain the viewer's logged-in state.

The problem arises when a user is being added (let's consider a successful entry). The snackbar displays the success message retrieved from the useSelector hook. However, if the page is re-rendered, the snackbar still shows the message, even if the user has not been added.

Section 2: Resetting Reducer State

To prevent unnecessary re-renders, we can reset the reducer state after performing actions like delete, edit, or create. This ensures that the useSelector hook only triggers re-renders when relevant actions are called.

Section 3: Implementing Reset Actions

First let's create a reset state in reducer:

export const addUserReducer = (state = {}, action) => {
  switch (action.type) {
    case "addUser-api-request":
      return { loading: true }
    case "addUser-api-success":
      return { loading: false, response: action.payload }
    case "addUser-api-fail":
      return { loading: false, error: action.payload }
    case "addUser-api-reset": //added new case returning empty object
      return {}                 
    default:
      return state;
  }
};

Now, dispatch the reset action in our ui page

///rest of code 
<Snackbar
  anchorOrigin={{ "bottom", "left" }}
  open={snackBarIsOpen}
  autoHideDuration={3000}
  onClose={()=>{setSnackBarIsOpen(false);dispatch({type:'addUser-api-reset'})}}
  message={snackMsg}
/> 
</>
)}
export default Page;

Now, whenever the Snackbar is active and closes after 3 seconds, it will also empty the object in the addUser reducer, effectively resetting the state. You can also reset all states at once, but if it is only necessary to reset one state, this is the recommended approach.

Conclusion:

Resetting the reducer state in React and Redux applications is essential for efficient state management and preventing unnecessary re-renders. By implementing reset actions and handling them in your reducers, you can improve your application's performance and ensure a smoother user experience. Give this technique a try in your projects and see the difference it makes!

If you have any suggestions for improving the code, please leave them in the comments section. If you found this post helpful, please like and share it.

Happy Coding!