In this blog post, we’ll learn how to create a custom React hook called useCookieEffect that allows us to handle side effects based on changes to a cookie value. This can be useful in scenarios where we want to trigger certain actions when a specific cookie value is set or updated.

Table of Contents

• Introduction
• Setting up the Project
• Implementing the useCookieEffect Hook
• Using the useCookieEffect Hook
• Conclusion

Introduction

As web developers, we often work with cookies to store and retrieve small pieces of data on the client-side. Cookies can be used for various purposes, such as session management, tracking user preferences, or storing authentication tokens.

The React useEffect hook provides a way to handle side effects in functional components. However, it doesn’t have direct support for monitoring changes in cookie values. That’s where our custom useCookieEffect hook comes in.

Setting up the Project

Before we dive into creating the custom hook, let’s set up a basic React project to work with. We’ll assume that you have Node.js and npm installed on your machine.

First, create a new directory for your project and navigate into it:

mkdir use-cookie-effect
cd use-cookie-effect

Initialize a new React project using create-react-app:

npx create-react-app .

Once the project is set up, open it in your favorite code editor.

Implementing the useCookieEffect Hook

Create a new file called useCookieEffect.js in the src directory and add the following code:

import { useEffect } from 'react';

const useCookieEffect = (cookieName, callback) => {
  useEffect(() => {
    const handleCookieChange = () => {
      // Get the cookie value
      const cookieValue = document.cookie
        .split('; ')
        .find((cookie) => cookie.startsWith(`${cookieName}=`))
        ?.split('=')[1];

      // Call the callback with the cookie value
      if (callback && typeof callback === 'function') {
        callback(cookieValue);
      }
    };

    // Subscribe to cookie change events
    document.addEventListener('change', handleCookieChange);

    // Clean up the event listener
    return () => {
      document.removeEventListener('change', handleCookieChange);
    };
  }, [cookieName, callback]);
};

export default useCookieEffect;

This custom hook utilizes the useEffect hook to listen for changes in the cookie specified by cookieName. When a change occurs, it retrieves the new cookie value and calls the provided callback function, if one is provided.

Using the useCookieEffect Hook

Now that we have our custom hook ready, let’s explore how we can use it in our React components.

Open the src/App.js file and replace its contents with the following code:

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

const App = () => {
  useCookieEffect('theme', (cookieValue) => {
    document.body.style.backgroundColor = cookieValue;
  });

  return (
    <div className="App">
      <h1>useCookieEffect Example</h1>
      <p>The background color will change based on the value of the "theme" cookie.</p>
    </div>
  );
};

export default App;

In this example, we use the useCookieEffect hook to listen for changes in the “theme” cookie. When the cookie value changes, the callback function is executed, and the background color of the body element is updated accordingly.

You can customize the hook and callback to perform any side effects based on your specific requirements.

Conclusion

In this blog post, we learned how to create a custom React hook called useCookieEffect to handle side effects based on changes to a cookie value. We implemented the hook and used it in a simple example to demonstrate its functionality.

Custom hooks are a powerful feature in React that allow us to encapsulate and reuse logic across components. The useCookieEffect hook can be a handy tool when working with cookies in React applications.

Feel free to experiment with the hook and adapt it to your specific use cases. Happy coding!

#react #customhooks