When working with web applications, it’s common to store data in the browser’s session storage. However, there may be cases where you want to perform certain actions or side effects based on changes in the session storage values. In this blog post, we’ll explore how you can create a custom useSessionStorageEffect hook in React to handle side effects based on session storage changes.

Table of Contents

1. Introduction
2. Setting up the Custom Hook
3. Using the Custom Hook
4. Conclusion

Introduction

React provides a built-in hook called useEffect to handle side effects, such as API calls, DOM manipulations, or event listeners. However, this hook doesn’t directly monitor changes in session storage. To overcome this limitation, we can create a custom hook that combines the useEffect hook with the window.onstorage event to track changes in the session storage.

Setting up the Custom Hook

Let’s start by creating a file called useSessionStorageEffect.js to define our custom hook. Here’s an example implementation:

import { useEffect } from 'react';

const useSessionStorageEffect = (key, callback) => {
  useEffect(() => {
    const handleStorageChange = (event) => {
      if (event.storageArea === sessionStorage && event.key === key) {
        callback(sessionStorage.getItem(key));
      }
    };

    // Add event listener to window.onstorage
    window.addEventListener('storage', handleStorageChange);

    // Clean up the event listener on unmount
    return () => {
      window.removeEventListener('storage', handleStorageChange);
    };
  }, [key, callback]);
};

export default useSessionStorageEffect;

The useSessionStorageEffect hook takes two arguments: key (the session storage key to monitor) and callback (a function to call when the value associated with the key changes).

Inside the useEffect hook, we define a handleStorageChange function that checks if the storage event is related to session storage and matches the provided key. If it does, it calls the provided callback function with the updated value.

We then add the handleStorageChange as an event listener to the window.onstorage event. Finally, we clean up the event listener when the component unmounts, ensuring no memory leaks occur.

Using the Custom Hook

To use the useSessionStorageEffect hook, import it into your component and call it with the desired key and a callback function that will be executed when the value changes. Here’s an example usage:

import React from 'react';
import useSessionStorageEffect from './useSessionStorageEffect';

const App = () => {

  const handleSessionStorageChange = (value) => {
    console.log(`Session storage value changed: ${value}`);
    // Perform additional actions or side effects based on the new value
  };

  // Monitor changes in session storage for the 'myKey' key
  useSessionStorageEffect('myKey', handleSessionStorageChange);

  return (
    <div>
      {/* Your app content */}
    </div>
  );
};

export default App;

In this example, we define a callback function handleSessionStorageChange that logs the updated value to the console. You can replace the console log with any custom logic or side effects that you want to trigger when the session storage value changes.

By calling useSessionStorageEffect with the desired key and callback function, the hook will now automatically monitor changes in the session storage for that key.

Conclusion

Creating a custom useSessionStorageEffect hook allows us to handle side effects based on changes in session storage values. By combining the useEffect hook with the window.onstorage event, we can easily track and respond to changes in session storage within our React components.

Using this custom hook provides a simple and reusable solution for handling session storage side effects in your web applications.