How to Build a Custom React Hook

React is an extraordinary library for building user interfaces, providing a functional approach to web development. As your application grows, you might find common functionalities that could be abstracted out into reusable components or custom hooks. Custom React hooks allow you to incorporate shared logic across your applications in a more organized manner.

In this guide, we will explore what custom hooks are, why they are beneficial, and step-by-step instructions on how to create them. By the end of this article, you’ll have the knowledge to build your custom hooks, enhancing your application’s maintainability and readability.

What Are Custom Hooks?

Custom hooks are JavaScript functions that use built-in React hooks but encapsulate specific logic for reuse. They start with the prefix “use” to ensure compliance with the rules of hooks and usually return a value or an array of values that can be utilized in functional components.

For instance, if you need a piece of state, side effects, or context, custom hooks can help isolate that logic into a single reusable function.

Why Use Custom Hooks?

Custom hooks offer several benefits:

• Code Reusability: Encapsulate logic that can be reused across multiple components.
• Readability: Improve the clarity of component code by isolating complex logic.
• Separation of Concerns: Keep your components lean and focused on rendering UI.
• Testability: Make it easier to test units of logic in isolation.

Creating a Custom React Hook: Example

Let’s build a simple custom hook that utilizes the useState and useEffect hooks to manage an API call for fetching user data.

Step 1: Setting Up the Hook

import { useState, useEffect } from 'react';

function useFetchUser(url) {
    const [user, setUser] = useState(null);
    const [loading, setLoading] = useState(true);
    const [error, setError] = useState(null);

    useEffect(() => {
        const fetchData = async () => {
            try {
                const response = await fetch(url);
                if (!response.ok) {
                    throw new Error('Network response was not ok');
                }
                const result = await response.json();
                setUser(result);
            } catch (err) {
                setError(err);
            } finally {
                setLoading(false);
            }
        };
        fetchData();
    }, [url]);

    return { user, loading, error };
}

export default useFetchUser;

This useFetchUser hook takes a URL as an argument and fetches user data from that endpoint. It manages three pieces of state: user, loading, and error. The hook will handle the API call every time the URL changes.

Step 2: Utilizing the Custom Hook in a Component

Now that we have our custom hook ready, let’s use it in a functional component:

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

function UserProfile() {
    const { user, loading, error } = useFetchUser('https://api.example.com/user');

    if (loading) {
        return <p>Loading...</p>;
    }

    if (error) {
        return <p>Error: {error.message}</p>;
    }

    return (
        <div>
            <h1>User Profile</h1>
            <p>Name: {user.name}</p>
            <p>Email: {user.email}</p>
        </div>
    );
}

export default UserProfile;

In the UserProfile component, we utilize the useFetchUser hook to retrieve user data and manage loading and error states effectively. The component re-renders automatically based on the state managed by the custom hook.

Best Practices for Creating Custom Hooks

Building custom hooks comes with its set of best practices that can help ensure code quality and maintainability:

• Use The “use” Prefix: Always start the hook name with “use” to adhere to React hooks conventions and ensure they work as expected.
• Keep It Simple: Focus on a single responsibility; a custom hook should serve one purpose and do it well.
• Use Built-in Hooks Wisely: Combine multiple built-in hooks within your custom hook to achieve the required functionality.
• Return Values or Functions: Make sure your hook returns meaningful values or functions for the components that need them.
• Document Your Hooks: Include comments and usage examples to ensure clarity when others or you revisit the code.

Advanced Custom Hook Example

Let’s explore an additional example where we create a custom hook to manage window size:

import { useState, useEffect } from 'react';

function useWindowSize() {
    const [windowSize, setWindowSize] = useState({
        width: window.innerWidth,
        height: window.innerHeight,
    });

    useEffect(() => {
        const handleResize = () => {
            setWindowSize({ width: window.innerWidth, height: window.innerHeight });
        };

        window.addEventListener('resize', handleResize);
        return () => window.removeEventListener('resize', handleResize);
    }, []);

    return windowSize;
}

export default useWindowSize;

This useWindowSize hook listens for window resize events and updates the state with the latest window dimensions. The hook will properly clean up the event listener to avoid memory leaks.

Using the Advanced Hook

Here’s how to use the useWindowSize hook in a component:

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

function WindowDimensions() {
    const { width, height } = useWindowSize();

    return (
        <div>
            <p>Window width: {width}px</p>
            <p>Window height: {height}px</p>
        </div>
    );
}

export default WindowDimensions;

This component utilizes the useWindowSize hook to render the current dimensions of the browser window.

Conclusion

Custom hooks are a powerful tool for React developers, allowing you to encapsulate reusable logic while keeping your component code clean and maintainable. By following best practices and organizing shared code effectively, you can make your applications easier to understand and work with.

As you continue to build your React applications, consider creating custom hooks whenever you find yourself repeating logic across components. With this guide, you have the foundation to get started on building your own custom hooks.

Happy coding!